If the front of the 1954-55 engine does not have the mounting holes, they can be drilled as follows:
https://www.stovebolt.com/techtips/engines/motor_mount_front/index.html
https://www.stovebolt.com/techtips/motormount_235.html

Engine to transmission no problem.
To simplify explanation use the bell housing, flywheel, clutch parts and starter from the 1956.
Chevrolet changed from 6 volts to 12 volts beginning 1955 2nd. This affects the number of teeth on the flywheel.

If the 1954-55 is a car engine, it will most likely have an automatic choke carburetor but you can swap that out.

The last change in the exhaust manifold design was in 1951 so you should be okay.
Check that the exhaust dampener works. Turn by hand, it should rotate and spring back when released.
If not you may want to swap manifolds.

I would make a cradle for the 1954-55 and test that it runs okay before installing.
Details can be provided.

Last edited by buoymaker; 03/20/2022 5:38 PM.
"Adding CFM to a truck will only help at engine speeds you don't want to use."
"I found there was nothing to gain beyond 400 CFM."