I would get a 8inch rear out of a mustang. the T-4 is the transmission type 4 speed manual. and rebuild kit your looking around 500 if you have tools. up wards of 1200 to 1400 if you have a shop due it. i have a 5.0L 302 with a c4 trans. Automatic. with a 85 mustang posi rearend thats the 8.8inch. works good. just make shure you get the roller rocker engine. or the power of aftermarket will not be good.