I finally got the chance yesterday to start working on the 81 Big Horn. It was not running when I got it, and I think I know why. Apparently, the ignition module failed, so someone decided to use a GM HEI module external to the distributor to get it to run. They also swapped out the original Mikuni carb with a weber, and hooked the fuel line off the return line from the mechanical pump to the tank with a inline reg on it. The PO claimed it ran like this, but I don't know how, and if it did, not very well. I am waiting for a new module before I fix the fuel line issue, and I will replace the hacked ignition module wiring with the right pickup and module. Why someone would hack up the distributor wiring for a 6 dollar part is beyond me...Will take pics when I return to it with the parts to fix it.