LT1Z28:
Welcome to the Mustang family. You'll probably want to change your user name at some point.
The T-56 conversion can be done. Check out
www.ddperformance.com They can help you out with that.
As for the biggest motor, if you've got the cash, well, you can put about anything into a Fox body Mustang and have it fuel injected. And, for the record, a 302 can be made to produce some good power with or without a power adder. Personally, I would like to have a stroked 302 (to 331) ProCharged terror of a motor - but that will be down the road.
Good luck and again, welcome!
E