A few years back I did a 3800SC swap and the guy insisted that he keep the Getrag. A month later, he split the trans case into shreds on a WOT shift. He replaced it then split the case again but this time in his driveway. That transmission was designed for a 2.8L and not for a 3800. application. What Nosrac has said x 2.
As for Intense Racing, they have been around a long time selling 3800 upgrade parts. While we have good reports on them, I lean towards ZZ Performance for my 3800 parts as they have a wider selection..
" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman 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 "