mustang II swap is very well documented, do a search. You can use a toploader or a C4 behind that 460, so the tunnel mods aren't necessary unless for some reason you decide to go C6. A C6 isn't necessary, especially in a little mustang. There will be lots of weight on the front end, and not much on the back, so it's gonna be tough to drive, and don't expect much in the way of traction unless you do alot of homework on suspension set up.