I was at the sand dunes all of last week.. I actually seen a 2jzgte in a sand rail.. I HAD to go talk to him about it and the motor was in a chassis originally built for 351 clevlend. He said it cost him bout 800 to get mounts fabbed up given it was in a sand rail so was prob.. lil stronger then a car would have to be. His motor was built as a sand rail motor eliminating all un necassary stuff like some sensor and what not... Was running an AEM stand alone.. puttin 700hp to the wheels in a 1900lbs car!!!!! YA it was fast.
As for your mustang it doesnt matter if it was setup for I6 or v8 mounts are the same. but youd have to fab mounts, driveline, tranny mount and more then likely regear the rear end to be a close match to the 2j setup. the electrical would be hell if u use factory ecu but it could be done but would DEFINATLY have to be an electrical guru.. even running a stand alone there would be some electrical that would have to be done.. the I6 in your car maybe has 8 wires total and the jz prob 50 That go to the chassis itself. and then however many hundred for the ECM. Then bears the question wit all that trouble why not 2jzgte?? That would be a wild setup though i gotta say.. If it were me id do it for sure!!!!
BTW... im doin a 1jzgte swap i ordered front clip today. out goes the 7mgte for a rebuild to bout 500hp and refit into a sand rail!!!!! OH YEAH!!