Nicely done kirsch....you are correct...not many diesel ADs....with the nv4500 you'll want to run a fairly low rear gear...not sure what you have in now...with a 26" rear tire and the nv with a .7od...and I'm not sure about what a 4bt does rpm wise... here's a rpm calculator.....
http://www.csgnetwork.com/multirpmcalc.html