First a little history on the truck. My shop truck is a '79 3/4 ton full time Chevy. It sat for 5 years rusting away when I bought it for $150 bucks. Fixed some minor issues with things here and there. Did some brake work and ended up replacing the heads. Major cracks in the old ones. Had to grab a fuel tank out of another truck to put in this one. Here's the deal, driving around in town is no problem. My shop is 15 miles on the dot from my driveway. When I leave in the morning almost like clock work 7 miles later the thing will start to chug. I mean CHUG! enough to were you can hear the slack in the u joints. Seems fuel related but not really sure. Switched out filters and swapped out fuel pumps. Checked lines for pinching and so on but nothing there. Pulled the carb apart and cleaned it up. Any suggestions? Similar experiences. Biggest part of the problem is it doesn't do it in town so nothing to check when I get to the shop.