After trying several of the formulas posted on this forum and not achieving the right fit I turned to the professionals. The reason that there is no universal axle fit for the auto swaps is because all swaps seem to have a side to side mounting variance of 1 " or more. WCF, Purple reign and custom mounts all seem to place the engine in a slightly different position. We measured positions on several 3800 swaps and they were all different.
The axles on my 3800SC auto swap were custom made by an axle shop. They use the GTP inner tripots, Fieros outer tripots and both GTP tripods. I am not sure what axles are used. We just held the control arm at road position and measured from the end of the outer tripods to the center of the inner tripot, gave the measurement to the axle shop and they did the rest. My axles now have a factory fit.
87GT - 3800SC Series III engine, 3.4" Pulley, N* TB, LS1 MAF, Flotech Exhaust Autolite 104's Custom CAI 4T65eHD w. custom axles
87GT - 3.4L Turbocharged engine, modified TH125H
" I'M ON THE LOOSE WITHOUT THE JUICE "