Ford Fuel System :: Idles But Dies When Throttle Applied?

I just rebuilt the Autolite 4100 on the 390 in the 62 T-Bird I just purchased. Starts up and idles great, but when I apply slight throttle, the motor shuts off. If I apply a lot of throttle quickly, it picks up fine and drives with no problems. No sputtering, or backfiring. I just slightly apply the throttle, the RPMs drop, and the motor cuts out completely. Starts right back up when I turn the key, but does the same thing, at any temp.

I originally thought it was a vacuum leak, but checked what few vacuum lines there were, with no leaks to be found. Hooked up my vacuum gauge and it read at a steady 15psi.

New mechanical fuel pump, haven't checked the fuel pressure yet, but I installed a see through inline filter, and it's filled up and pumps fine.

Timing is at 8 degrees, and vacuum advance is hooked up to the only vacuum line in the carb. New cap, rotor, plugs and wires.

I adjusted the idle mixture screws down until the idle dropped, then turned them out a half turn (I've read on here it should only be a 1/4 turn, so I'll adjust that later today). When I was messing with the carb yesterday, I noticed the inlet check ball retaining screw was leaking a bit of fuel, so I went over the carb and checked all the screws and tightened down what needed it.

When I rebuilt the carb, I left the original needle & seat assembly, since they were in great shape, and the ones in the rebuild kit were much smaller. The choke plate needs to be adjusted, as it doesn't open up all the way at full temp, but the engine did the same thing with the plate held open all the way open.

I've gone through everything else I think it could be, so I'm figuring it's the carb. This is my second carb rebuild ever (first was a Motorcraft 2150) and it went smoothly, and I double checked the floats and measurements.