When I start out in first and rev up the truck it is really rough. But once the RPM is above 1500, it feels like I could pull a train with my 292 2bbl. I have the carb and ignition set to factory, when there is no load in neutral it sounds great when I apply some RPM. But trying to get to 5 miles an hour is a huge struggle. I have no firewall, so I can hear it sounds like popping in the headers maybe? Once rolling its a sweet ride with no engine probs. Thanks

 

Either you are flooding or your ignition timing is off. It is also possible to be way too lean.

Does your exhaust smell rich? Have you set your valves?

 

You have no firewall??

Are your cab mounts rusted out?

Timing is a good suggestion. Unless you know that the damper is good, you can't know that it is timed right according to those marks. The damping mass, on which are the timing marks, can slip over time. The result is it looks like it's timed right but it's not. Try adjusting the timing without a light and see if it improves.