Major work dude. the biggest problem you would have once you manage to tear out a huge piece of firewall to make room for the tranny is chassis flex. The car was designed with the torque from the engine going forward and backwards, not side to side. Your only hope would be a tube frame with scort sheetmetal. after you deal with getting the engine and transmission in then you need to deal with the front suspension. a 400 small block and a th400 behind it will ad a boat load of weight to the front. the rear end will also weigh more as the tranny sits behind the engine instead of beside it. not to mention you will lose you independant suspension on the rear unless you can figure out a way to bolt on say the rear end of a late 80´s supercoupe. the ones with the supercharged 3.8 v6. these had a great rear end setup for hanging turns. If all you want to do is go fast in a straight line ie. drag racing, punch the block a full mil, call JE or Weisco and get some custom dished pistons, stroke it, get goood head and exhaust. Add a turbo with a little bit bit of nitrous to move it along. When the block is in for the machine work have them o-ring it to help out under high pressure. Bolting in a 400 will cost you plenty and you may very well get tired of it. But hey, like old man Dan always told me "If you got the money buddy, we can maker ´er scream!"