NV4500 is like the bigger brother of the NV3550.
the 4500 is used in alot of the Chevy and Dodge V8 trucks. If you are up for a bit of reading - here are a couple of good web pages for you;
http://www.nv4500.com/
http://www.high-impact.net/transmiss...ear/nv4500.htm
My NV3550 is cactus - rather than getting it rebuilt im putting in this which is about the same length, size etc - but is alot beefier than the NV3550.