New Body and Paint

Do you always strip to bare metal to paint your project?
Seems as though you could sand and block the original paint and prime to proceed if it is sound.

For me it depends on the condition of the metal under the paint. My Barracuda I sanded the original body and parts, primed, blocked, sealed and painted. My current project had rust issues so I am taking it all down to bare metal and using epoxy primer, sandable primer, block seal and paint. That is my method anyway.

That's what i was thinking.
If the original paint is good but worn thin or faded sanding properly and priming should be a good starting point.

That is a catch 22 for sure. Most old cars have been painted at least once in it's life by now. You will have rust to deal with. Plus the new paints do not play well with the older stuff. So you never now how they will play together until they get together.

You can do what you want, but I would never paint an older car without stripping down to bare metal. I would consider allowing the current paint to serve as a base for a paint job on a newer car, because it will be painted with modern Base/Clear paint. But you have no idea what is under the paint on a 50 year old car. There could be three layers of three different types of paints, crappy rust repair, super bad body work with 1" of Bodo poorly applied. You won't know if you just paint over what is there. In my humble opinion, don't do it.