[Sizzler]

It's going to be a dyno engine only, running in a limited (low) rpm range.

I wouldn't get all exotic.

4.25 bore x 4.125 stroke, loose bearings, sideoiler block not important unless that's the only one to go 4.25 bore.

More important would be the intake and head porting. Should promote low-rpm flow and some work as needed on the exhaust port. Proper cam selection, electric water pump.

Tunnel ports and SOHC heads work outside the range, except I don't know if maybe they might not be needed given the displacement.