Sorry, I did not elaborate on why I brought up my old issues.

My 68 starved for fuel quickly after I got her home. The seller had swapped the fuel pumps twice and thought the pump was the issue. The *real* issue was that there was a ton of crud on the tank. It would clog a filter up very quickly and the pump would be "dry." I put a renewable filter before the pump and it would clog up every day. After a week or two, I had filtered out quite a bit of gunk and I started going a few days, then a week or two before needing a cleaning. Finally it was flushed out and I thought it was fine. That's when the busted pickup tube in the tank began to cause me to run out of gas at 6 gallons...

In both cases it looked like the pump was failing, but removing it and pumping the lever showed both pumps to function just fine. If you've checked the the pump's interior and it all looks fine, then I'd say a clog is your issue.

As George suggests, pour some fuel into the carbs and see if it runs fine.

I've been told that (like the AC pumps with the glass dome), the early pierbergs have a filter screen under the metal dome. You said yours was not a peirberg, but you might check for an internal screen just in case.