I have a 93 w/302 and had the same problem. It would stall at a stop light on occasion but if I put it in reverse it stalled nearly all the time. I finally talked to a trans shop and found out that this is common due to the trans filter falling off.
It's appearently a problem with most filters not fitting properly. I went through everything else including a TPS, ignition modual and other parts. The new filter did the trick. I had taken it to another shop and they told me I needed a trans rebuild for about $900. I called a different shop and they came up with the filter problem. It cost me about $100. to get it fixed. | 
