Ryan 4 psi in the pump is to low 7 psi is in the ball park much more than that and the seals in the carb wont hold it. Also I did not see it was 35 gal. per hour pump I have serious doubts if that volume is going to be enough to feed that engine at higher RPMS. I would get a fuel pump that I know is appropriate to this engine, like replace or rebuild the original, do not forget filters, if its been sitting for a while that could be a problem, make sure you have good gas going to the engine. Look at the plugs and replace if any question on them, then comes the distributor cab and rotor, make sure they are clean, in good shape and all contact points are clean and not corroded, emery cloth works good to do this. Plug wires are another component that needs to be in good shape also. Most of these fuel pumps are pretty easy to rebuild as long as you can find the parts. I would get all the numbers off the carb and start at my local auto parts store and if they have nothing then I would start with the military truck sources like Memphis equipment etc. if they dont have a rebuild kit for the carb and or fuel pump they might have replacements for yours. Make sure your electrical component is of the truck is good, then I would tackle the fuel pump if that does not cure the problem I would tackle the carb, carbs get blamed for a lot when actually its not usually the problem, BUT this is an OLD truck and as we all know everything deteriates over time Ryan Keep me posted but it sure sounds like fuel, especially when your in 3 gear and just starting to work the motor a little, start with fuel first!
KK
