You can reliably get the engine to backfire if you are running down the road, cut off the ignition, and cut it back on.

So it is possible that you have a loose connection at the distributor or coil that is causing an intermittent spark. Your coil could also be going bad.

I don't know why you are running an 8V battery, it should not be necessary if your connections are good n tite.

Other things to look at would be your vacuum advance at the distributor. Does it move when you rev the engine? If the diaphram is busted in the advance, you will have a vacuum leak, and of course it won't run right either. You also might want to check out the centrifical advance in the distributor, and the health of the distributor in general.

Hope you are not running the truck in a closed garage.

I too am from NC and "GO State"
NCSU grad, 1977

Kurt