drum to disc conversion

[sduckworth13]

I just recently bought a 1967 GMC 3/4 with manual steering, 8 lug drum/drum manual brakes and rear leaf springs w/o coils. I have been reading everything on the conversions and everyone says that the engine crossmember will bolt right up from 73-87 with just a few bolt hole mods. I went out and bought a complete suspension from a 1974 1/2 ton with disc/ drum. I bought the entire suspension which has 5 lug disc up front and drums in the back , steering ( steering wheel, gear box, idler arm, centerlink etc. and brake system ( lines and prop valve too). I didnt get the pump just figured I would buy a new one, along with hoses too. I was wondering if someone would guide me to what I can actually use for the swap. My questions are can i use my 3/4 ton crossmember and just swap the 1974 1/2 ton suspension or do I need to swap the entire suspension with the crossmember attached ? Can I swap the rearend out of the 1974 and use it ( leaf springs w/o coils) ? Can I use the power booster/ mstr cyl from the 74 Chevy 1/2 ton on my 1967 3/4 ton without any modifications to my firewall ? Thank you