Truck stalls and I've tried all the obvious fixes...

[bjgreine]

I have a 1971 Chevy Cheyenne with a 350 crate motor. I purchased the truck 6 months ago, and have been working out a lot of its "kinks." My current issue is that it stalls. It occurs when I am at a stop and try to accelerate. Sometimes I can't get it out of the neighborhood, sometimes I drive it around but it struggles most of the time, and sometimes I drive with no issues once I've passed the trouble spot. What I mean by trouble spot is that I've figured out I can very slowly accelerate and once I get to 20 mph or so it will drive regularly. When it is acting up, hitting the gas too hard causes it to die, then I can't start it for 5 to 10 minutes. I have put a new quadrajet carb on it, new mechanical fuel pump, replaced the fuel line from the pump to the carb, replaced the inline fuel filter (added by previous owner due to rust and debris in gas tank), and checked the carb filter for an unexpected clog (even though it's new). It also has new spark plugs. I run 93 octane gas, and have run a few rounds of fuel system cleaner during the first few months of owning it. During the first 5 months of ownership, there was never even a hint of this issue. My fuel gauge doesn't work, so the first time it happened I thought I may have forgotten to fill it up the last time I was supposed to. Any thoughts?