What kind of motors fit nicely?
That's another question where the answer will be subjective and depend on what someone thinks nicely means.
I suppose any motor you could ask to hop into the engine compartment, and which responded by nicely fitting in.
I've seen GM V-6's, and Chevy small block and big block V-8's installed in S-10 framed trucks.
I know Joe has a 425 Cadillac in his. And I'd imagine most any sidemount type motor, including the later GM inline sixes could easily be adapted.
But what does fit nicely mean?