[scary gary]

Well after a lot more research online and using offset and fitment calculators, I went ahead and ordered the adapters. Yes, they are 2 piece. The 5x5 and 6x5.5 patterns share a stud. I was going to swap rotors and axles, but since the offset is so high, I would have to use a spacer. And, I still may do that down the road. I'm aware that adapters have a bad rep.. but I've driven over 100K miles with knockoff Dayton adapters that people have told me are very scary. In my experience, you just need to keep an eye on them and make sure they are tight.
I really just wanted to see if I can get them to fit my Blazer and still be able to lower it.
Here's are some photos of the adapters on my Blazer, the wheel mounted, and the wheels with 255/30s mounted on my friend's lowered 87 c10.
Looks like I'm going to be able to lower it. I have no problem trimming or rolling the fender lip if needed. They seem to clear the rear fine, and do not rub anywhere on the front when turning. I'm really excited