If all you did was R&R the trans (nothing else) the first thing I would check would be the neutral safety switch. Fords are right on the trans shift linkage, not sure on Chrysler. On Fords you can diconnect the harness to the switch and run a jumper across the two wires for the neutral start circuit and try and start it. If it starts you know the switch is bad. Just a guess.
BUILT FORD TOUGH