My friend has a rx-7 which he has tactically destroyed trying to make fast. He is going to part it out and I might be able to get a hand on his turbo kit. It is a greddy t-78 turbo. Do you think it would be possible to set this size turbo up on the 4.6l mustang?
Sure. All you need is to build the exhaust plumbing to allow the thing to spin. Set up an oil feed and return, build yourself a new intake tract, and fabricate whatever bracketry is required to relocate accessories that are in the way and you are home free!
On a more serious note, to learn a little about what it takes to do homemade turbos like this, check out www.toohighpsi.com