I forgot to add that it's a stock points-type distributor with a crane cams electronic conversion. The timing was set by a local speed shop owner because I cannot physically access the timing marker window on the balancer. My alternator is in the way. I'll have to pull the alternator and the bracket and actually possibly the battery box will still be in my way to then try time the engine with a light. We were unable to take it for a test run that night or I would have discovered the issue. In neutral it revs freely to 5500+. In gear, I hit a wall. I know I do need a better distributor, but I was planning to drive it like this for a little while. I know the inability to get a light on it makes it tough. But he had it humming that night so I really thought it was good to go.
He didn't record or at least tell you the advance curve numbers? If the engine rev's freely and aggressively responds to throttle in neutral without any bogs or holes from inadequate initial pump shot?.. then I'd still put money on this motor having ignition based issues. Another thing to look at is float levels. An engine under load takes far more fuel to accelerate the car than just winging the throttle. So, you could be going lean enough in gear under load to act like this too. Vac advance pot can easily be tested by sucking on the end of the distributors vacuum advance diaphragm hose(off the manifold end) then plug the vacuum created with the tip of your tongue. Sounds funny but it works well for simple functionality testing if you don;t have a handheld vacuum pump. If the pressure drops away after a bit then you have a leak in the rubber diaphragm within the housing.
Maybe try rechecking the points gap and close it up a little. You will need to reset your timing again, but I have experienced to bigger of a gap to break down under load before
