3.08 to 3.73
 

I can't remember all the conversations around gear swaps. Can I pull out my 1/2 ton open 3.08 12 bolt rear and dana 44 front end and install new 3.73 units into same housing? Does someone like Randys Ring and Pinion sell good new units?

All you need are gears to fit your 3.08 carrier. I would suggest getting some richmond gears. I don't think you can get thicker gear sets for the D44 though.

TTT
 

Can I just swap complete 3rd members? Or do gears need to be setup again?

I wouldn't go cutting tubes and all that, its not worth the trouble just to change gears. In order to change the gears in the D44 you may need to get a different carrier for it. For the 12bolt rear you can get gears that will fit your current carrier just fine. I think you will have trouble finding a set of whole 1/2 ton axles with 3.73 gears, most of them had 3.08 or 3.42's.

I don't think swapping whole third members would be any easier at all than just swapping gears. To swap the hogs head your going to need to cut the tubes off put in new hogs head, make sure their really straight and weld them back. But if you pull the carrier out you will have to re-set the gears anyway.