425 Super Rocket fit in a Cutlass Supreme classic 88 and if so what all would I need to change

 

The 425 is exernally identical to the 455, and lots of those have been swapped into G-body Cutlii. The biggest problem is that the 1967-older motors have a different crank flange bolt pattern, so you will need the correct flywheel. Also, use the G-body frame pads and motor mounts from the 307. Use W/Z exhaust manifold or the G-body BBO headers.