Just a note for you guys who are assuming that the fuel pump is OK. That's not necessarily true. Just because it runs when the key is on says nothing about what type of pressure it's putting out. So far dave is the only one who has said show me the pressure. My first step would be to check the shift linkage for proper adjustment. Second is to test the fuel pressure. Third, check the codes.
Perhaps the wiring on the new transmission is different, and the compooter isn't getting the correct codes, so it's tripping the neutral-saftey switch and the engine won't start thinking the tranny isn't in Park or Neutral.
Who needs a road...if there's a perfectly good JEEP trail somewhere else!?