The PCM on my 3800SC is located behind the driver seat on a tray on the firewall. I did trim the heat sink ears on the connector side about 1/2" maybe 2" in length for rear seat clearance. While I can't recommend this procedure and I wasn't sure that it was going to work, its been working for four years with zero problems. Subsequent swaps that I did have the PCM as Ryan mounts them, behind the console. That's a far better place to mount them but early on I didn't realize that there was enough room there.
" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, 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 "