Question on Donor Car

Why use donor car buy a crate motor or lots of 273's around? Parts 65 and below would work better as ma mopar was making changes after that. I would put a 318 in car lots available and adaptable motor mounts ect easy to find. I did that in my 65 cuda makes more power easier than 273 and more parts for less. Once car is no longer original its unhindered by such standards. I painted 318 to look like 273, used 273 wrinkle valve covers, air cleaner ect most just asume its a 273 until I pass them...hahaha! Do as you please only one to satisfy is your own need for speed. Plenty of rebuildable radiators ect..go for the gusto! Bueno Suerte