I have an '81 J10 with the 258 and muncie 4-speed, it also have very low gears in the axles, I dont know what the axle gears are since there are no tags on them. My question is, I have a camper that is about 4000 that I would like to tow, and I am not sure if the truck is up to it. I have ungraded to a Offy dual plane intake manifold and 500 cfm Edelbrock 4bbl carb. The truck runs great, and I know I have put 1100 pounds in the bed and it pulled just fine. But I am trying to relate poundage in the bed to tow weight, before I just hook and go. Any body with any experience on something like this, I would like to hear your input, thanks.