Think about this. Several years ago there was someone locally with a 66 Mustang. It should have had a 289. He pulled it out and put in a scruby 305. Plus he had little bow ties cut into the rear lower valance next to the back up lights. He was taking it to all of the shows and proud of the fact that everyone was mad at him.
The common excuse around here regarding people swapping everything out for scruby engines is because they are so much cheaper to build. But to stuff in a SBC you have to first fab some motor mounts. Then you have to do something about the tranny. Then the drive line will be wrong either in length or the slip yoke or for the u-joints. Yeah, the SBF might be cheaper to build but what about the downstream costs. I understand it's "YOUR" car and you can do what you want but I am a purist. I prefer them how they were built.