I had one of those but it was a step side, with a 300 6. the fuel line was too close to the manifolds and would overheat the gas in the fuel line leaving air bubbles in it ,starving the engine till it stalled. The fuel tank was under the seat and the filler was on the corner post next to the door handle. After it stopped running it wouldn.t start on it's own unless I popped the cap and blew really really hard into the tank , to force the fuel to travel toward the carb again... and that was with with a foil wrapped fuel line. That truck was a beast in it's day ,rust ultimately took her from me, but the 300 was still strong.