Help! I have a 64 suburban, i'm converting it to 4 wheel drive, I want a 5 speed manual transmition. I know little about the NV3500 or the NV4500 except that the housings are differrent. One is aluminum and one is cast iron. I want to use it with a np205. However I wonder if it will work with a 203, because I currently have one of thoughs. I just really want to know which one is better? Thanks alot!