Ordered a Pertronix distributor not because I think it was part of the problem but just because I like the idea of updating that part. Blocked the line from the fuel tank and ran a line to a container of fresh gas as was suggested but in doing so was surprised to find a frame mounted fuel filter in the line that I didn't know was there. It was kind of hidden behind the vacuum tank. After working for an hour or so I got the filter canister loose and, though there was no filter inside, there was the ugliest collection of debris you could imagine along with liquid (gas?) the color and consistency of muddy water. Took the whole thing loose and threw it away. Now, with the line to a gas can, the truck runs fine. Still think maybe the fuel tank is part of the problem so may replace that just to make sure. Thank you all for your help and suggestions. It's nice to know there are folks out there willing to help.
