Do a seach for D&D performance and on they site it will tell you everything you need to know. If you want to save yourself money go with a T600 Tremec the gear ratios aren't to far off from that t56.
You can get everything installed assuming you know how to do the trans yourself for $2300. T600 holds up to low 9s.
Take a look at this:http://www.stangnet.com/pbullitt/tremect56/ Also the new 2005 Ford racing catalog has a trans mount to put a T56 into a GT. It's from the 2003/4 Cobra for $41.