Well for that kind of power output your on track with building up the suspension but you'll have to have a whole new trans and a well built 8.8 rearwned. I would do 31 spline axles with c-clip eliminators. Sinse you have to do all that I'd just get a rear end out of a 94-95 GT and build that. A t-5 trans won't hold the power either. You'd probably want to go with a built c4 automatic. Dont forget the aluminum drive shaft also.
You can't lose if you put God first!
1989 LX, 306 with TF top end kit, Anderson N-21 cam, TKO 600 trans with steel splatter shield,full Maximum Motorsports Mustang maximum Grip box, Detroit locker rear end with 31 spline Moser axles. Staggered wheels with Nitto 555 315/35/17 out back.