[Daniel U]

I called Midwest Transmissions who had a YouTube video on the NV3500. The person who answered was able to designate from the casting number (GM 867 9097) that the transmission was from a 92 C1500.

1991 NVG 5LM60 (late NVG= New Venture Gear
1993[1] New Venture Gear releases the NV3500. Externally the earlier GM units look like the NV3500; however the internal components were extensively redesigned.
The HM290 and 5LM60 units have a complicated arrangement of 4 shift rails. The NV3500 has one shift rail.[2]
There are two designs for the 5LM60 input shaft and bearings (input shaft and main shaft). The first design 1988–1990 has a ball bearing with a roller bearing behind it. The second design has a much larger single ball bearing. The first design bearings are reputed to be failure prone.[3] The updated input shaft and bearings carried through to the NV3500.