There is a lot more to the swap than dropping the motor in, some examples are a new k member and motor mounts. Also you will need a gt wiring harness and ecu. And no you cannot reuse your t5 because the bellhousing bolt pattern is not the same.
Bottom line, a lot of work will need to be done but it can be done. My advice, though, would be to sell your current mustang and buy a gt.
07 GT Tungsten Gray
02 GT Mineral Gray
98 Crown Vic P71