I think the shifter will line up, based on articles I've seen about swapping T5s into first gen 'Stangs. I know you'd need a different bellhousing ('79-'83 Mustang, or Tremec), and the driveshaft yoke is probably different. You might have better luck in the classic tech room, at least some of those guys have probably done the reverse swap.
__________________ 1992 Deep Emerald Green Mustang GT Hatch, 5 speed, 2.73s, Mac fenderwell cold air intake, '93 Cobra MAF, Mac 70mm throttle body & spacer, Explorer intakes, Mac unequal headers & offroad pipe, Magnaflow catback, Walbro 110lph fuel pump, Jet adjustable FPR, MSD Blaster coil, Accel 8mm wires, FRPP aluminum quadrant, UPR firewall adjuster, stock cable, Granatelli upper control arms.
Waiting to go on: Granatelli lower control arms, and GT40 Iron heads! | 
top loader in a 86 mustang? 
