I may not be the right person to ask about this, I consider myself a novice and a young buck in this hobby compared to some of the others that were around when these cars were created and know alot more about them than me.
When I bought my car, it was a 68 Coronet with a 318 and 25,000 original miles, no rust, and all the paperwork. Everything original was still on the car, other than the air cleaner. I changed out the intake, carb, and got an air cleaner. Then went the valve covers, exhaust manifolds, points and condenser. I also replaced the front drums with discs and the original steering wheel with a much smaller diameter one.
While I was doing this, I kept doubting myself and asking should I be doing this, or should I leave it original. I met a friend that is a Mopar enthusiast and was around when these cars were made. He gave me the advice of : It's your car, do what you want with it. And I did. I kept all the original stuff in case somebody ever ended up with the car and wanted to restore it back to its original condition.
The other piece of advice I was given by him and another friend who is a Camaro enthusiast was : all the stuff I was doing is making the car more driveable and more fun to drive, and this is the same stuff hotrodders back in '68 would be doing if they had the car and the aftermarket there is now.
Whether all this is true, or not, I don't know. I think it is all a matter of opinion. But I don't regret anything I did, cause I'm happy with my car. I say do what you want with it, as long as you're going to be happy with the outcome.