kewljay, I cannot thank you and everyone else here enough. It almost is looking like this is something that I cannot do in a weekend. So here is where I am.

They did make a (get this) 2005 Silverado 1500HD which had the 6.0L and 4L80E engine. But I'm not finding anything on the transfer case that was in there. I'm still researching though.

I found a j/y trans for $750. I figured that I might as well completely replace the transfer case with a new one (it's 225K on the truck... I think it might be time). It never dawned on me to see if they made a manual transfer case for the 2500HD since mine is a manual (floor mounted) shift, which I have to be honest, I prefer. I guess does it matter? If the 80E's transfer case is only electric motor driven, how much work is it to wire up the dash selector switch? I think (hopefully) this is one of the last questions I'm going to have until I start buying stuff. To solve the drive shaft issues, I'm going with a new drive shaft from Denny's. I want to go with a new yoke, front and rear shafts.