Small parts aren’t the problem.
Transmissions and engines are. Small blocks are still semi easy to acquire, depending on where you are, but in another 10-20 years it won’t be.
I can do a small block carb swap into my fuel injected 4 banger jeep easily enough if I wanted. Hell I can swap a ford lima 4 banger into it easily enough, but try doing an amc swap that’s not a gm bolt pattern or a ford engine into your GMs. I have a vast range of engine options due to the jeep aftermarket and amc’s love of gm motors that GM doesn’t have.
“I have a vast range of engine options due to the jeep aftermarket and amc’s love of gm motors that GM doesn’t have.”
You clearly don’t know how large the GM aftermarket is. Heck, even the flathead Ford market has suppliers.