GM ran the NV3500 behind V8s in half tons till at least 05, likely until the body style change in 07.5.
There are a number of different versions of each but they come in the earlier style external slave and 96+ internal slave. The updates made throughout it's lifetime range from minor shift rail changes to complete cluster shaft updates.
I can't remember the exact year splits, but the stongest transmissions are from the 4.8L trucks from 99-07.5
The 96-99 internal slave transmissions are next best, but ther is a single shift rail version and a version with multiple shift rails like the old ones, the single rail model is preferred.
There are two versions of the external slave, one with a single piece cluster shaft and one with a cluster shaft that can be disassembled. I am fairly sure that it is the single piece one that had problems with falling out of gear and premature failure that gives the NV3500 it's bad name.
As you mentioned, all fullsize NV3500s are 32 spline with an integrated 6 bolt round pattern t-case adapter cast in. The mini truck NV3500s are 27 spline but have a 5 bolt round pattern adapter and have their shifter located a good 5" further back then the fullsize rigs (which are a good 5" further back then an SM465 in themselves) with much weaker internals.
NV3500s are not super tough transmissons like the 4500, but they are not the weak garbage that most people tend to spout out on forums. Many fail due to people filling them with gear lube or ATF. They use a 5w30 weight fluid with an additive package for the syncronizers and will fail quickly with other fluids. Many fail due to leaks that go un-noticed or ignored too. They only hold a couple three and a half ounces of fluid and that can dissapear quick through a leak.
I really like the gear spacing they offer, and have enough faith in their strength that I am pulling my early low ratio NV4500 in favour of a 3500 from an 04 that had a 4.8L
