Cant afford a 4x4 but am curious if getting a setup to lock both rear tires when climbing a fairly steep hill while pulling my trailer would help or if anyone has a rear locker?
If you're currently having problems climbing the hill, and just spinning one tire alot, then a locker should help as long as it's a straight climb, you don't want to make very many turns with the locker engaged.
locking the back axle will help with the traction but its gonna lower your MPG, unless you invest in something like an air locker. i think another choice could possibly be a heavier duty LSD, you just need to weigh the risk vs benefits which in this case are cost vs getting stuck
Get a Tru-Trac for the rear. It isn't a true 'locker' but will have MUCH better street manners that a full locker such as a Detroit. I would not waste my time with the "drop in" lockers, such as a Loc-rite, behind a high torque diesel. I've seen a bunch of them break in Jeeps and Samiras.
I don't think I would want to tow heavy loads with a Detroit in the rear as it would really work out your R&P as well as your axles when turning.