86 c10 brake upgrade 1.00 to 1.25 question

[obrut]

Hi, I have a 86 c10 2WD shortbed with the 1" front brakes. I would like to lower it and have been doing a bunch of searches to figure out what I want to do. I just bought a set of flip brackets from board member specialtyretail and I was going to do drop spindles and cut one coil from the stock springs.

I found a set of belltech drop spindles for sale locally for a decent price. They guy said they were off a 81-87 2wd c10. He said they are stamped 31200. From what I've read this could be for 70-72 or 73-87 trucks. Either way they use the 1.25 rotor. He also has new 1.25 rotors, calipers, backing plate and rubber hoses they he will include for a little more money.

My question is;
To convert from 1" to 1.25" brakes I need the rotors with bearings, calipers and rubber hoses but what about the proprotioning valve, master and booster will mine work?
How can I tell if the spindles are for 73-87 and not 70-72?
These will work with the factory 15x8 rallie wheels right?
Anything else I need to know if I do the swap?

Thanks,
Tim