Need help with auto trans

I have two Ram 50's, both '87, both 2.6L engines. One has a 5 spd., the other has an auto. The 5 sp. runs fine, but body is poor and frame is less than good. The auto has a poor engine, but body and frame is much better. I (my son and I) pulled the engines and trans on both, put the engine that was on the 5 sp. on the auto, and put the engine and auto back into the auto truck. Engine runs fine, transmission does nothing. It will lock up in park (can't move vehicle) as expected, but does not engage in forward or reverse. In forward or reverse the vehicle can be moved.
When we first put the engine/trans in place, we forgot to put fluid in the torque converter and we ran it for <5 minutes. We then pulled the trans, filled the torque converter and reassembled. No change in status. I later found out that when we (my son) put the transmission back in the second time (after filling the torque converter) he filled it up until it said "full," but put in only 3 quarts (1/2 full....). We then filled up the transmission with the proper amount, still nogo.
LInkage is working - but no indications that anything is happening inside the transmission. When we pulled the transmission the first time, fluid looked good and unit was shifting just fine. We pulled the pan and put a new filter and gasket on. No evidence of any kind of residue or damage...
Help!
When we first put the engine/trans in place, we forgot to put fluid in the torque converter and we ran it for <5 minutes. We then pulled the trans, filled the torque converter and reassembled. No change in status. I later found out that when we (my son) put the transmission back in the second time (after filling the torque converter) he filled it up until it said "full," but put in only 3 quarts (1/2 full....). We then filled up the transmission with the proper amount, still nogo.
LInkage is working - but no indications that anything is happening inside the transmission. When we pulled the transmission the first time, fluid looked good and unit was shifting just fine. We pulled the pan and put a new filter and gasket on. No evidence of any kind of residue or damage...
Help!