hey, i am thinking of buying a 27 ft from the late 70s with no motor.
it is set up for a chevy 454, Question

whats the difference in a long block chevy 454 for the street and a marine 454?

i know the cam is different, are the valves and heads differenet tooo but im guessing the blocks are the same correct?

Piston to wall clearance should be set up looser
Cam difference.
Brass feeze plugs.
Spark protected ignition, starter, alternator.
Marine carb with J tubes.

Those are the main differences.

ok, and what if i were to swap a gm diesel motor, the 6.5L basic gm motor? or a cummins? should i just buy a ready to go marine diesel? or would a street version do the same job?

i would have to get a new transmission for a diesel?

A pick up diessel is different from a true marine diesel. Way different. I wouldn t even try that. totally different animal.

if you ran a seperate closed cooling system, you might be able
to get away w/ the truck diesel-but I wouldn't bother unless
you were gonna go with a duramax! and that would cost ya
some coin!