Please help small to big bolt pattern

Hey guys a newbie here, I have found this site very helpful I found a member through here Mark that I had the pleasure of purchasing rebuilt 4 piston KH through. Long story short I do not wanna cut the car up and I am looking for the biggest tire in the back.

I have done a fair amount of research and have been digging around the forum and it seems like you can go a few different ways.

First I just put new pads, rotors, calipers, master, and all new stainless lines up front. Maybe I should have went a different way to achieve BBP but I have seen a few people talking about sending in rotor hub to moser, they list redrill for 90 bucks. Am I correct in thinking this for the fronts.

Rears- I have seen alot of great things on doctor diff I am thinking an offset kit for the leafsprings, rear disc brake kit and BBP axles. Is their important details i am missing here? I also plan on calling Cass as I've heard and talking this through as I've heard he is very helpful. Any suggestions here please let me know.

End goal run 15x4 up front 15x8 with a 275/60/15 radial in the back. 4.5 in backspacing and for the record the wheels I have looking to run are the jegs spikes. From what I have seen people say that is the max size for stock tubs maybe roll the fender lip. Should this in theory work do I have to worry about any front clearance issues with redrilled fronts. Thank you in advance for any knowledge.

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