I've had the same problem with an 83 245. I went through and replaced both pumps and filters. My tank had some rust problems that where plugging up the main pump and the filter was like mud water. But that didn't solve it. I found one of the nipples on the intake manifold without a tight fitting cap. I replaced that and it helped some. Replaced the intake manifold and sensor under 4th intake. Still when I start the car it will start fine and then after a couple seconds if I don't give it some gas it will die. Once its warmed up the thing will drive fine. I replaced the Idle Control Valve with a new one this week hoping that it had something to do with it but no help with the stall although the car runs better.

My next thought was actually the large hose to the throttle body. But fuel delivery is also my next direction seeing it feels the same as when the pre-pump is going out and you have some power with a sudden loss but it quickly regains on and off. I've unhooked the AMM and it still does the same thing with a wondering idle and stall. Hopefully this may help get an idea of what it is not going to be. Although every problem could be different but it sounds very much the same.