4300 lbs sounds low to me... I think the auto's got a bad rap personally... I'll be the 1st to say that I hate them but mine has been pretty good since I've owned it. I beat the crap out of my truck and the tranny has held up pretty good to my abuse. I'm not sure if the PO rebuilt it or not but I picked my truck up with 120k on it and now with 155k its still going strong.

http://www.apsprecision.com/ has fixed all of the problems that the tranny's have and can build you a bullet proof one to match your needs.

if your going to get a auto dodge, bypass the radiator tranny cooler and add the biggest you can get infront of the radiator since your going to tow with it. the cooler the fluid temp is, the longer the tranny should last.