My mild 440 also had a small stumble that was minimized by adding more initial timing (14 initial, 36 all in) and sitting idle mix to max vacuum. I alsobought the tuning jets and rods, installed a A/F bung and tuned to A/F. Then I swapped the 915 heads and iron intake with Eddy Performer heads and a CH4B manifold. Car starts and runs/pulls hard. But when I stomp on the gas it goes completely flat/lean for a sec, then must get a burst ofgas and goes balls out.. It makes me lurch forward it is so bad. I bought and installed the .043 squirter and a new accelerator pump,but have not tested it yet.

I am ready to buy a Quickfuel 750 and be done with it, but am bummed as I have the finelines stock fuel lines..

Good luck solving yours. Check initial and idle mix with vacuum gauge.