[73kay]

I would think if you use the stock/s10 frame but box it and get heavier duty suspension that would work better. I think it boils down to drivetrain and suspension that you need to really address. The stock 3100 is roughly 3000 lbs so it would be a good think to try and get some more weight on the tow vehicle. Especially if there aren't any trailer brakes. (Scary).

As a side note, I have towed with my 4Runner a trailer (1500 lbs) and a half ton truck (3500 lbs) about 5,000 lbs and that's the 4runner's limit. Even with trailer brakes my load can get kinda scary. It just haves too much influence on 4Runner. And the 4Runner weighs almost 5000 lbs so your getting close to the limits of a half ton or less equipment.