Modern cars are great and all, yet (to some) they lack a certain "spirit," so to speak. All that technology and driver aids make skillful driving a job for the on-board computers, rather than whoever's behind the wheel. Where's the best place to escape this? Well, classic cars, of course!

But while these classic beauties may be perfect "drivers' cars" for every gearhead, owners need to be able to recognize which ones should be modded and which should just be left stock. Sounds simple enough? Well, not quite... And failing to recognize if your classic car should be modified can have embarrassing consequences. We're talking completely ruining the car's value and image.

However, countless classic car enthusiasts still insist upon modifications, while others see them as sacrilegious. And while many of these cars are fine to be modified, a few are in the 'no-go' zone. In this list, we elaborate on 10 classic cars that should NEVER be modified and give you 5 examples of classics that are actually improved by mods.

RELATED: Flexing Muscles: The 15 Meanest And Baddest American Cars Of The '60s And '70s

15 Keep It Stock: Ford GT40

Nostalgic look at ford gt40
via Motor1

Anybody who's seen the Oscar-winning film Ford v. Ferrari knows just how hard Carroll Shelby, Ken Miles, and Ford worked on the victorious GT40. For the time, it was the best the world could offer.

Today, although it may not be as quick as the new ones, the Ford GT40 still reigns as Ford's greatest race car! As far as we know, nobody has been courageous (or dumb) enough to modify a real Ford GT40. Then again, those who can afford one are probably too nervous to touch it anyways.

14 Keep It Stock: Toyota 2000GT

Via: Wikipedia

Those who've claimed that Japan doesn't have an expensive, classic car comparable to those in Europe are just plain wrong. Case and point, the 1960's Toyota 2000GT. Nowadays, one of these beauties will set you back over $1 million, and that's just the low-end. A couple of owners have modified them for on-track performance, but one committed the ultimate sin; engine-swapping one! At least it wasn't an LS engine...

13 Keep It Stock: Bugatti EB110 SS

via Flickr

The uninitiated among you may have never even heard of the Bugatti EB110 before. Nevertheless, it's still a Bugatti. One which possesses a lot of power, a great design, and that classic Bugatti pedigree. As such, the EB110 SS should be regarded as a piece of history, not a tool for tuning companies like Mansory to toy with. Nope, the EB110 SS is fine as is.

RELATED: Bugatti Pays Tribute To EB110 With 1600-HP Centodieci

12 Keep It Stock: Aston Martin DB5 Shooting Brake

Via: Reddit

The regular Aston Martin DB5 is already a unicorn on its own. Though, imagine what regard the Shooting Brake edition is held to. "Shooting Brake," in short, is another phrase for "hatchback" or "wagon." Instead of waiting for a customer to chop their baby up to make a hatch version, Aston went ahead and did it before them. Maybe they were trying to keep up with Ferrari's Breadvan and its competitors, too.

11 Keep It Stock: Shelby 260 Cobra

Via: CLASSIC.COM

Like the DB5 pictured above, this Shelby Cobra is no regular Shelby. The 260 Cobras were a part of Carroll Shelby's first batch of AC Cobras (the one pictured here is the first-ever built; the CSX 2000). If a modded Cobra is what you want, then get a kit-car. For the sake of every car enthusiasts, please don't dare to upgrade an original one.

10 Keep It Stock: McLaren F1

Via: Autonews

Want to know what a masterpiece of human engineering looks like? Look no further than McLaren's greatest achievement; the McLaren F1. It's not just a classic sports car, but a classic supercar! Made with real gold and Formula 1 technology, the McLaren F1 broke a litany of records, such as speed and price. Ask yourself, do you really know more than a McLaren/Formula 1 engineer? If not, then leave it be (excluding the McLaren LM packs).

9 Keep It Stock: Porsche 959

Via: Tom Hartley Jnr

Every bit of this car is made to be lighter, more advanced, and quick! Instead of hindering the cars reliability, the Porsche 959's CPUs became the backbone of its success. God save anybody who tries to take it apart, though.

RELATED: 15 Car Mods You Aren’t Allowed To Have In The US

8 Keep It Stock: Mercedes-Benz 300SL Gullwing

Via: The Drive

We couldn't forget to include the Mercedes-Benz 300SL Gullwing (convertible, too). Being fast is cool, sure, but the 300SL Gullwing is also a rolling work of art! Every angle, every curve, and every tiny detail is perfectly formed together to produce (perhaps) the most stunning vehicle in existence. That being said, don't "fix" what isn't broken.

7 Keep It Stock: Lamborghini Miura

Via: RM Sotheby’s

Lamborghinis, compared to brands like them, are often modded by an incredibly large amount of buyers. Tons of aftermarket parts are built for the Aventador, Gallardo, Huracan, Urus, and so on. However, few exist for the Lamborghini Miura, since it's already perfect.

Designers at Liberty Walk made a wide-bodied Miura not too long ago, yet, that was just a kit-car. Even Liberty Walk knows not to mess with the Miura, and they wide-body everything!

6 Keep It Stock: Ferrari 250 GTO

Via: Motor1

Does much really need to be said about the Ferrari 250 GTO, along with the rest of Ferrari's GTO model? Of course not, these vehicles speak for themselves; both in terms of historical significance and cost. The highest recorded selling-price for a 250 GTO is $50 million+. Knowing that, you'd have to be literally insane to try to mod one, let alone drive it more than once in a blue moon or afford it to begin with.

5 Mod It: Nissan R31 Skyline Turbo

Via: Driver Motorsports

Although this particular Skyline series doesn't have a GT-R version, the Turbo alternative is the next best thing. Similar to the other Skylines, the R31 loves to be tuned. A few owners have pushed some serious power out of the Japanese machine, improving the appearance along the way, too! Don't let the R32, R33, R34, and R35 overshadow the real O.G.

4 Mod It: De Tomaso Pantera

Via: art.branipick.com

The De Tomaso Pantera is the, sort of, Ugly Duckling of Italian sports cars. That doesn't mean it's bad looking, just not the most well-built sports car to come out of Italy. With some modifications, though, the Pantera comes alive. The boys at Fast N' Loud proved as much with their badass (restored) white Pantera.

RELATED: 15 Classic Cars That Were Donked Out (And It's Disturbing)

3 Mod It: Datsun 240Z

Via: Vintage Car Collector

Next up is a JDM classic, the Datsun/Nissan 240Z. The 240Z, as well as the rest of Nissan's Z-series, are astounding cars to modify. The 240Z, however, is the crème de la crème of the lot. Judging by some of the tunes we've seen, it's hard to believe that the old Datsun is almost fifty-years-old. The best part, though, is its affordability.

2 Mod It: BMW E30 M3

Via: Drive

It's no secret that the E30 M3 is widely considered BMW's awesomest vehicle to date. The stock setup is sublime, but has room for improvement. Since the E30 M3's production, BMW has increased the quality and power of their M-performance engines, which is why E30 M3 owners frequently swap in newer, larger, BMW engines. The wildest one we've seen is an S85-swap (V10) from a BMW E60 M5.

1 Mod It: Corvette C2 Stingray

Via: Pinterest

Before you Corvette aficionados freak out, hear us out. Yes, the stock Corvette C2 (especially the split-window) is a gorgeous muscle car. Now, imagine what it would look like/do with the right upgrades. Our favorite example is the lowered red model from Fate of the Furious, driven by Letty for the eighth installment.

NEXT: The 2020 Volkswagen e-Bulli Concept: A Classic Is Reborn