Lowering a 1-Ton Crew Cab

[Twisted Liquid]

I have a 1979 GMC 1 ton crew cab dually that I have lowered using Belltech 3" spindles and 4" shackles in the rear. The truck has quite a bit of "rake" still and I am trying to figure out how to level the stance out.

Does anyone have experience lowering these older trucks? Can I go any lower with stock leaf springs, de-arching, or is the only answer to use airbags? Is there a flip kit available for these trucks. Seems to be strictly half tons for flip kits. I don't want to sacrifice all my load capacity as I plan to use the truck to tow moderate loads occasionally. Any help is appreciated.