Engine stops running after put in gear

[Moabdude]

I have a Plymouth with a 318 engine and a 904 automatic transmission.

The engine runs fine when it is in Park but a soon as I put it in drive the engine gives a "puff" and stops running.

Sometimes I manage to get the car rolling but as soon as I hit the gas pedal, again a puff and it stops running.

Any suggestions?

[GregWeld]

I'd start by checking the timing. It sounds like it might be retarded and doesn't have enough power to even hold idle with ANY load.