Thanks for the latest input!

After going through all the steps yet again, and a reinstallation of the old torque converter, lo and behold, I have pumping and shifting again!!
I can only ascertain at this point that what was mentioned earlier is correct - although the TCs appeared to be the same, perhaps the bolting was such that the pump was disengaged with the installation of the new TC.
So, long story short - days of agony and numerous quarts of fluid only to end up where I started.
If anything, I guess this goes to prove that you need to double and triple check what someone gives you, to be sure it is the correct part.
You guys are great!

PS - After reading through many of these posts, I am now considering changing out the valve body and/or solenoids, to see if that gets rid of the trans occasionally "slamming" into gear and the O/D light flashing - but I'll wait a bit first to see if this latest fluid flush and fill made anything better or not.

I gotta ask, while I'm here: what is the difference in size between the standard and the Heavy Duty TC in these vehicles, and how do I know which one I have? Would that have made a difference in this particular application?