Converting 1980's 2wd 5 lug to 6 lug

[D13]

I swear I've seen part of this before but just can't seem to put it all together.

I have several late 80's 2wd trucks, with both thick and thin rotors. I'm becoming annoyed at the limited rim and tire options of 15". The 16" 5 bolt rims are not common (ie cheap). So what i was looking at was swapping to 6 lug, allowing access to the full range of late model rims and a wide tire selection.

In the front, CPP sells 6 bolt disc rotors that are direct fit to the factory spindles. Given they fit all the way back to 73, am I correct in assuming these are the thicker version?

I belive in the back I can use a 4wd axle to get six lug, correct? Moser sells replacements with 6 or 5 bolt patterns in 28 spline, but only 5 bolt in 30 spline. Wouldn't the K5 and K10 Burb 89 up be 30 spline 6 bolt?

From what I have seen this pretty much eliminates the ability for inexpensive discs in the rear. Didn't GM have such a package on some 8.6 axles recently? What's different in the rear axle that makes it not a bolt on?