I did this upgrade on my '87. Used Seville Calipers, bleed valve mounted up. Grand Am Rotors, Seville pads ( slightly modified), Stock parking brake cables work, but using Pontiac 6000 cable on one side makes the fit easier. Combined with Grand AM front upgrade, no proportioning valve needed. I did upgrade the Master Cylinder and the RD bigger brake booster.
Here's a thread that may help http://www.fiero.nl/forum/A...130314-2-083566.html
'87 GT , '00 3800 Series II SC, 4t65e, Vue Power Steering. (SOLD)