1992 to 2005 Dodge New Venture NV4500 5 Speed Manual Transmissions were built with two Identification Tags, that if present, will tell you what the transmission assembly number is. The assembly number will tell us what parts your particular transmission has which is important given the number of NV4500 variations there is. A stamped metal ID tag is secured to the transmission using two of the left PTO cover bolts. There is also an ID decal on the top cover.
Many transmission rebuilders remove the factory ID tags during the rebuilding process. If the transmission was rebuilt for the original configuration and installed in the year and model truck the assembly is specific to, no problem. It is when a transmission is either rebuilt for different applications or installed in different model and/or years that problems start. A quick example is installing a 1996 NV4500 4x4 Diesel NV4500HD transmission into a 1997 truck. Externally, the transmissions from both years look almost identical and they are in fact externally interchangeable, but internally the two years have different gears and gear ratios. If you order a 1997 countershaft, it will not fit the 1996 transmission.