72 gmc, power booster? lowering? what can i use?

[ampline]

i am new to this site,,, and i have alot of questions... i am trying to learn exactly how to use this site??? regardless i recently bought a 72 gmc long bed, and i would like to upgrade the brakes a bit... it has the front discs, and i am fine with the drum rears... but i would like to add a power booster.. the question is.. can i use a different year besides 67-72 gm power booster? if not... does anyone out there have one? or any info to upgrade the brakes??
i would also like to drop the truck a bit, perhaps 3 in front and 4 in back... or 4 and 4? or something along those lines... it has those helper springs in the rear,, so i figure i will still keep some payload if i just block the back? do i have to buy drop spindels for the front? or how much should i cut off factory springs? should i buy new shorter springs? i am on a budget,,, but need to keep the truck drivable. it is my work truck... anyway.. i have a lot of questions,,, any help or info would be greatly appreciated... thank you.