I have a 1972 Challenger that nothing is original to it so I am doing a restomod and cleaning up some of the things I hate. One is the side markers that were stuck onto it as an afterthought to placate the DOT. These are flush to the body from a 1971 Roadrunner.
Definitely one of the best things about having a non-collectible car... You get to mod it to your liking. Nice improvement. It is going to stand out in the crowd.
I like looking at the original cars but they never did steer or stop well. The modifications I do to the car are for my edification and won't add much value except for the parts. And we all know how hard it is to sell a car based on that.
Upgrades to a driver, like a brake upgrade are definitely needed for safety. Just save old parts if you are worried about resale value. These items are just a bolt on.