Laying frame 68 C10 need help

[ls1chevy]

hey guys i need some help!!!! im new to this site and im starting my new build its a 68 c10 swb and im planning on laying fame on 20s in front and 22s in the rear. im gonna be doing all the work myself in the drive way i have all the tools. but the thing is ive never bagged a truck before and feel like its going to be a head ache ive searched around and tryed to gather all the information i could find but im still not sure on a few things. i know that im going to need a dropmember up front because i dont want to have to z the frame. im going to keep the stock control arms up front for now and im doing a 5 lug conversion with 2.5 drop spindles. i have the slam specialties Re-7s 7inch for the front and the bag plates on the way from suicide doors im also going to buy there step notch for the rear.

Questions:

am i going to be able to lay frame with the stock trailing arms in the rear?
and should i use a 7 inch bag in the rear or 8?

and getitng that low what about the pinion angle?

i have many more questions but its late so ill ask later

anyhelp on this would be great. thanks