Update: I kludged two broken/bad E4ODs to make one not-bad trans. Unfortunately, when I did the test drive, it wouldn't make the 2-3 shift. Even after I checked the shift-body and accumulators, and swapped the solenoid pack.
I suspect that the torque converter was not 100%
Since we knew what was wrong with the trans that went bang, I took the whole OverDrive planetary assembly from the first attempt, to replace the carnage. The torque converter from the trans that went bang was reused...and it worked. Well, works for now. It passed the trial run. Loaded up pretty good too. Exercised all the gears, took some hills, got it up to highway speeds.
Is it me, or is it really difficult to determine the transmission fluid level of a E4OD in a van?