Floor modifications will obvisously depend on how your engine/trans is being mounted in the frame. If you are subframing it you might find you have to raise the engine up to provide fuel pump clearance as I did. If you are using the stock axle or a MII set up you might not have to change a thing unless you move the motor mounting back for better weight transfer. My modifications to the floor are slight to provide transmission clearance. I fabricated a custom hump from some extra 18ga laying around. Total height at the front is about 2" and it tapers down flush at the rear before the seat. I plan to have a custom console coming down from the bottom of the dash to the floor so this slight elevation will not even be seen.
If you cut out th eold firewall you might be able to use the recessed area of that one to start your own trans tunnel.
