well,well, somebodies been out having fun
When you say all forward gears are lost; is that with a manual-VB?
If reverse still works, then the following items are still working; the pump, the hi-drum, and the L/R band.
If both manual-low, and reverse, only get you reverse; then the hi-drum is piled up and the forward clutch is leaking pressure big-time.
If with a manual VB, you cannot get second or third, then the forward clutch is not working at all.
So,you may need a piston in the forward clutch (called rear by Mopar) and then a major overhaul kit with bands, and sprag kit.
Then;some 4.30 gears, a chassis weight reduction program, and put the teener back in,lol. Ok just kidding, about this last part.