Maverick stalls

I have a 1974 ford maverick with a 250 straight 6cyc. Automatic. Lately I have noticed the car began to run rough, but now everytime I put my car into gear and press the gas the car stalls. However, I noticed that if I just let the car coast in drive with out pushing the gas eventually the car will finally stay running. Noticing that I had a fuel leak around the fuel pump I decided to change the pump however, this did not fix the problem. I also adjusted the timing, fuel mixture, idle speed, changed the oil, and replaced the fuel filter. This still did not fix the problem, so I checked for vacuum leaks. Again the problem still remains. If you have any sugestions they would be appreciated.