Why do you have a ? after the 5? How many speeds does it have?
It's pretty easy to properly identify an NV4500. It'll be a two piece unit, in other words the bellhousing and the case are two separate parts - not integrated like some of the light duty 5 speeds. The case is cast iron, will have an aluminum top cover. It has a PTO cover on each side (similar to the 4 speed Muncie SM465) but is considerably larger than the SM465.
Here's a pic of an NV4500 out of a '96 C3500:
Here's one from a '94 3500HD so it has the longer tailshaft/housing and parking brake attached to it:
In case yours is actually a 4 speed, it'll be the Muncie SM465...note it's got those PTO covers too but is clearly a shorter transmission (length wise). The last few years of SM465 have an aluminum top cover too but that's just from probably '87-up as they were being phased out, most you see are the old ones with cast iron cover.
Richard