I have used a faucet wrench with great results. You remove the rear facia (an easy 20 minute job) then go into each frame, hold the nut with the one way faucet wrench, and turn the bolts from below, preferably with an impact wrench. Works every time but just make sure that you have a support jack under the cradle.
" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Powerlog manifold, Northstar TB, LS1 MAF, 3" Flotech Afterburner Exhaust, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, HP Tuners VCM Suite.
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "