[Zoomad75]

Mating a NV4500 to a 205 can be done a couple of ways. Main factor is which version of the 205 to you have? figure eight mounting pattern to the t-case adapter or the more modern 6 bolt round pattern? Also depending on the trans you are coming from the spline count on the input is different. The TH350's and 700r4's have a 27 spline output where the TH400, 4L80e and NV4500 have the 32 spline output.

Changing the input in the 205 to get the 32 spline input is pretty easy. ORD could set you up with that pretty quickly.

Depending on the T-case mounting style you have will make the biggest influence on what you do to mate them up. The figure 8 style can only be mated by using the Advance adapter housing. It replaces the stock output housing which also contains the 5th gear and synchro. You end up cutting some where close to 3"-4" off the stock output shaft and replace the problematic 5th gear retaining nut with a split collar the bolts over the shaft.

The better option and the one that does not require the output housing/shaft modifications is to find a 6 bolt round pattern 205 case. They were used up to 1991 and are otherwise similar to the earlier figure 8 cases. That case will bolt right up to a 4500 without modifications.

Next issue comes down to Clutch type. All 4500s used a hydraulic clutch. The issue here is the early gmt400 trucks that used these transmissions had a external slave that was on the passenger side of the engine since those trucks had a driver's side drop t-case vs the earlier solid axle GM trucks that had all been driver side drop t-cases. Guys have made them work, but there isn't much room for the slave and the front driveshaft at full stuff on that side. The next option is the integrated slave style 4500 that had no external slave but a more modern integrated slave/throwout bearing that eliminates the need for an external slave. No issues with the passenger side driveline but will require getting the plumbing for the line to match up with a 84 to 91 clutch master and line.

I didn't happen to notice which engine you had for the 71, but since the 4500 came behind conventional small blocks and the later LS engines you just get what you need based on the engine. Gen 1 small blocks just need a flywheel that can handle an 11-12" clutch which is very standard and not hard to get. People don't always remember that the NV4500 was an option for 3/4 ton and 1 ton GMT800 trucks with a 6.0 L for few years. Rare for sure, but it's the way to get the right thickness flywheel to deal with the difference in the amout of the crank sticking out the block which is less than the Gen 1 small block. They were 10 spline inputs like always. So all you need to do is spec out a flywheel for a 2002 3/4 ton Chevy or GMC with a 6.0 and a 5 speed. Also order the clutch based on that and which version of the 4500 you have.

I'm swapping to a 4500 when I do my 8.1 swap in my 91. I'm planning on using a later style 4500 with the integral throwout bearing. The most difficult part of that will be the clutch pipe plumbing.