So one of the last things that I needed to move from my original motor to my donor motor was the torque converter. Unfortunately, my son tried to help and stripped off the heads of the bolts -- the bolts that are already WAY hard to get to, on the inside between the transmission and the torque converter. So now I am wondering two things. First, should I just buy a new torque converter (and which one) and second, how do I know what transmission I actually have in the car -- a C4 or a C6?

I don't know squat about autos but here is some info. You can see there is a difference in the pan shape for easy ID. Did C-6s come in EBs? I know C-4s did.
http://classicbroncos.com/tranny-c4.shtml
http://classicbroncos.com/tranny-c6.shtml

Are we talking converter-to-flexplate nuts or flexplate-to-crankshaft bolts?

Well. I guess maybe I am not really sure. If you are looking at the transmission on the ground, with the torque converter on the right end, between the end of the transmission housing and the torque converter there are 4 or 5 bolts that have heads that face the transmission. The only way to get to them is with a deep offset box wrench. Noew that they are stripped I have no idea what to do.

The thin metal flexplate -- looks like a metal gasket -- is loose (and bent), and I can't get it off w/o taking off the torque converter.

I'm still confused. Can you put up some pics?

Sure, great idea. I can probably do that tonight.

HAH! I just realized I was describing it wrong! DOH! I am talking about the bolts that go into the TORQUE CONVERTER that are between the ENGINE and the TORQUE CONVERTER. But I will post some pictures anyways. My bad.

Ok, here are several pictures. Let me know if these help.

Ok. The converter nuts are holding you up. Roll the motor over until you can get to the open space in the blockplate at the bottom. You should be able to get a socket or wrench in there. If the nuts are too rounded just cut them off. A new converter and flexplate is only about $100.

Ok, very good. Thanks! If I was going to buy, do places like WH and the like sell those parts or would I have to get them somewhere else? And should I worry about getting a "Heavy Duty" torque converter --if there is such a thing?

Unless you are running a radical engine a stock converter is fine. Bulkpart has the cheapest converters and flexplates. You need to know engine balance and tooth count for the flexplate, input shaft spline count and bolt pattern for the converter.
http://www.bulkpart.com/Merchant2/merch ... y_Code=C-4