The 68-72 can be used as a truck. Just have to beef up a few things.
I have a 68, and knew I would use it for light towing, so built a high torque 350 (.020 over) with a 4L660E out of a Suburban for the trans withy a stand alone controller. Has a 3.36 ten bolt in it right now, but I recently bought a 3.31 12 bolt to put it. Plan to upgrade the rear brakes to 11 inch drums before installing the 12 bolt.
Put big brakes on the front using Corvette rotors, a modified 69 and later caliper bracket, 76 truck calipers and re-using the old drum brake spindles (modified).
Secondly, put the air shocks back on (came with them from the factory). I just got a vintage "JacPac" set up so that I can raise and lower the rear from inside the cab. BTW, I will be selling the rear air shocks that came with the kit, as I believe they fit a 67-72 Chevy C10.
Third, install cargo coils in the rear.
Lastly, boxed in the rear frame rails and installrf a hidden trailer hitch.
Short write up on the hitch here:
http://www.chevelles.com/forums/43-e...ler-hitch.html
I hauled a 7800 pound load with this set up without any issues. Didn't have enough air in the rear shocks, so the rear sat down just a bit. That issue will be resolved when I install the JacPac kit. Even with the rear down a bit, it drove perfectly.