I like to see the old street rods with correct brand engines. A model A with a Flattie or even a 289/302 is a good choice. Mopars get a Mopar engine. A friend built a 38 Dodge coupe and used a B body Cordoba as a donor car. Everything he could use including the power windows went in the old sedan.
i'm with you there. exception to the rule is that hemi's can go in anything and european cars are fair game. i'm about to start on a volvo 142 that's getting a 2.3L eco boost motor for a client. should be fun!
i always like seeing stuff that would be "period correct", like a kid got a 10 yr old car and snapped in motor from something that would have been current then. say something like a 56 plaza with 273 commando/4spd or 413 wedge and an art carr bang box 727.