one thing i would do is get rid of the "rear/differential" axle and go with a straight axle (find a trailer with round tube and 6 lug) or you can get the hubs and spindles ...
http://www.etrailer.com/Trailer-Hubs...-213-5UC1.html .. ( the spindles that fit are on the same page in what people bought with the hubs) and build your own to fit with 6 lug to match your truck (assume its still 6 lug) some states do NOT allow rear axles to be used one reason is that no one keeps up with the oil level in the diff. and the next thing you know things tend to lockup... the other thing you want is the tongue as long as possible/feasible the longer the tongue the easier it is to backup and the better it follows