When a rubber engine/trans mount is 25+ yrs old it's usually in need of replacement. Agree with using rubber mounts although I use poly mounts and twin dog bones on my 3800SC. While the engine sits solid, you do feel vibrations at idle but at road speed I notice no difference. If the engine is stock rubber mounts are the way to go. .
" 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 "