69 GMC 6 lug drop questions.

[NCannon]

Hate to start a new thread here but I just can’t quite find what I’m looking for. If I’ve missed something where this is discussed, any pointing in the right direction is appreciated.
Truck is a 69 GMC fenderside long bed with 6 lug wheels and the I6 (if that matters).
I’d like to keep 6 lugs, and drop it roughly 3.5-4” in the front and back. As it sits now, it’s about 1/2“ lower in the back.

Front:
I don’t think I can (nor do I want to) cut the coils in the front to get the 4” of drop, so I’ll need to go with drop spindles. As I understand I’ll need to go to discs if I go to those drop spindles. I’d prefer to maintain consistency with my lugs and not have ½ of them be ½” and the other have be 7/16”. I’m also comfortable buying new rotors and just knowing they haven’t been turned excessively, they aren’t warped, or anything else I can’t check at the junk yard. Meanwhile, I’m trying to keep costs reasonable, so I’d like to pick up as much as I can from the local pull n’ save. The problem I’ve run into is that so many of the trucks here in the Denver area are 4wd, or the lugs are the wrong size, or they aren’t 6 lug, or any number of issues. I’d like to know if I can pick up the drop spindles and rotors from a supplier, and then get calipers/lines/proportioning valve/MC from a truck in the junk yard that didn’t quite match the lug specs for a direct swap. If so what fits that description?

Once that’s done, I’ll probably just go 2”-3” drop spindles and cut a coil (or get 2” drop springs and new shocks). Can I still keep my 15” rally wheels if I go to discs?

Rear:
I want to just go spring under in the rear, but from what I’ve read it looks like it’s usually more than the 4ish inches of drop I’m looking for. I’d be perfectly happy with a little rake since I use this truck as a truck (I just had 1000lbs of concrete and wood in it last weekend, which lowered it about as much as I’d like). I’m thinking a decent option would be to go spring under but get some heavy duty springs. I’d see the 4.5-5ish lower from the spring flip, but then gain a little back from the non-old/clapped out springs. Again, new shocks as well. For the rear, I just don’t know if there are good donor trucks out there for these springs? I guess I’m okay buying new leafs, but I’d rather just pick up something that will work from the junk yard.

Any help is appreciated, again, sorry if I couldn’t find these answers in a search. Thank you.
-Nate