Well I'm building pretty much what you are after right now. 81 k10 long box on 12" suspension and 3" body and 44" sts's.
First off I'll say I agree with everyone saying its not very practical. It's stiff as a board, really high center of gravity, and in MI at least can't drive it legally on the road. Stupid lift laws
But for me I've always liked the obnoxiously tall truck cause I think they look cool. Other than that it's about useless

. And I only intend on playing in the sand dunes with this truck not rocks, mud, trails, etc... So not as big of a deal for my needs.
Quick run down of what I have into my lift and what I need still
Already have on truck
12" front super lift springs - $200 used
8" rear super lift springs - $200 used
2wd box - $50 used
Crossover for my D60 from fourwheelsupply.net - $234 new
Stainless steel extended brake lines and all fittings - $170 new
Still need
Drop pitman arm - $70 new
Diy4x shackle flip for 4" more in rear - $185
Hydro assist -

don't know yet
Driveshafts -

don't want to think about that yet but should be pricey
So far I'm $1109 into it with still the assist and drive shafts to worry about yet so I'd figure realistically I'll probably be $2500 - $3000 into lift, hydro assist, and driveshafts.
Lifting it is the cheap part. Making everything work right being so tall, that's where it gets expensive

I'm in too deep to turn back now.