Hemi in a '57 Shoe box car? Excellent! Ha Ha, way better than seeing yet another run of the mill Vette motor in there, that's been done way to many times already. I do enjoy seeing an perfectly period correct small block in a shoe box car, especially a rare Fuel Injection model.
Ford flat head in a '57 Chubby? Uh, no, that won't work. Rat Rod? Perfect!
I saw an early 50's Chevy (I never did care much for that particular body style myself) with a small block Ford in it. OK, at first I was a little startled, but then I just had to chuckle, 'cause THATS something you don't see everyday. The intense metal flake gold paint job was ridiculous though... BIG flakes of gold in there.
Some combinations are good or even great, other's, eh, not so much.