Hey guys and gals. Here's my problem. I just replaced the head gasket on my 91 fbird 305 TBI Auto trans. Once I got the timing right it fired right up and ran good. Unfortunately when I tried to put it in gear it stalled. A few hours later I thought I'd try it again so I fired it up and put it in gear and to my surprise it didn't stall. However when it warmed up it stalled when I shifted into reverse or drive. I checked and made sure the vacuum lines were all attached, even replaced the worst of them in the process of putting it back together. I put only 2 gallons of anti-freeze in it. Should it have been more, and could this be the problem? It didn't overheat. All other fluids are good. Any help you could give would be great. Thanks!

EDIT - I did notice that the oil pressure sending unit next to the oil filter was broken. Could this be part of the problem?