Is your idle too low? I am not much of a carb guy, but I just helped my neighbor out with this exact issue. The car would first idle low in neutral, then when he put it in gear, it would stall out. Raised the idle some, and the issue stopped. Then it started when he would turn his wheel, without giving it gas, and the car would stall. I adjusted the idle once again, and it worked like a charm. Its been over 2 weeks and his car hasn't stalled once.
Also, how are your plugs, wires, coil, distributor/distributor rotor and fuel pressure?