[78 GHOST]

You might have a clogged "sock" which is a nylon filter which slides onto the end of the fuel level sending unit. You can diagnose this by buying a length of fuel hose, and connecting a fuel can to the hose, effectively providing another fuel tank.. drive it and see if it's any different. I'd suggest using a fuel tank out of a small outboard powered boat, kinda made to not spill fuel everywhere.

To change the sock, you must drain the fuel from the fuel tank, lower the tank and remove the retaining ring to pull the sending unit.

Once you've got the sending unit out, you can grab the retaining ring which holds the sock on the end of the sending unit and twist it off. You need to replace the sock as it keeps sediment out of the fuel supply.

Other ideas, I recently found a problem with the engine under load only, caused by a faulty coil. Swapped out the coil for a good oil filled unit, and voila' problem solved.

A slipped timing chain will cause major problems.

A vacuum leak.

A debris fouled fuel filter at the carb.

Points old and crapped up.. out of adjustment.

Having a shop tell you "things are fine" doesn't really help us too much. If you can provide some basics such as the actual timing, vacuum you're reading, etc. we can help nail things down.

Personally, I only suspect an accellerator pump if the engine initially stumbles, then catches and runs fine. Your description sounds like a loss of power regardless of how much or how long you hold the pedal down. Is this so?

Typically, an engine will run like crap as a result of a lot of things being just a bit out of whack. Plugs are a little crappy, points are a little funky, filters are a bit dirty, engine suffers a few vacuum leaks, etc.

Personally, I'd suggest starting at the basics and going from there. You might need to borrow or buy a couple of essential troubleshooting tools and try your hand at fixing things yourself.. many shops aren't really good with these old vehicles anymore. You need a timing light, an Ohm meter, a vacuum gauge, a spark plug socket, plug gapping tool, and. These tools will help you determine the basic health of your engine, a compression tester is useful later if you eliminate the basics first.