I just finished an M465 to NV4500 conversion on my 1978 GMC 2wd R3500 dump truck and can shed some light on this swap. I used a 1995 4500 out of an R3500HD 2wd but did not want to convert my truck to a hydraulic clutch as the hydro assist pump system for the brakes (which works great with heavy loads) took up all the firewall room. The 1995 NV4500 does NOT bolt to the M465 bell housing, bolt pattern is wider and actually goes beyond the confines of the original bellhousing. I used a steel Lakewood scatter shield, used a boring bar to turn the guide hole to fit, drilled and tapped the bellhousing to the 4500 and backed up the threads with welded bolts. I used the original 40 lb. flywheel, new original 10 spline 12 inch clutch and did not modify the bellhousing in any other way, tranny flange to block is the same between the 465 and 4500, input pilot, throw out bearing shaft, 10 spline all the same. Used the HD clutch fork from the 465 bellhousing, drive shaft had to be shortened 4 3/8 in. U-joint is the same size. The end result is a perfect upgrade to an older very serviceable R3500, 1.08 5th gear helps out my 4.56 gear ratio rear to achieve highway speeds while the wicked low 1st gear helps me start out at my loaded GVW of 13,000 lbs. Who knows this may actually get my 10 bolt engine up to 12 mpg (empty). The challenge I have now is for a speedometer, I am still trying to figure out how to convert the electronic speed sensor on my new tranny to the old mechanical spedo in the truck, the least of my worries. Hope this helps someone.
