Different bag questions

[hbaublit]

I have read through over 100 pages of threads and I haven't found my answer to my questions, however I have found a lot of other interesting stuff.My questions are
1. What is the thickest lowering block I can run in the back?
2. I have a 10" step notch, do I need to weld a crossbar on the front or back or both on top of the notch? or neither?
I see some guys putting their bags on a bracket that is welded on the bottom of the axle housing and the top on the crossbar on the notch instead of on the trailing arm.
3 Is this a better setup than on the trailing arm? Or does it just get you lower?

My setup
1970 Chevy Step side C-10
Plan on buying Dominator 2600 for the front
Plan on buying Dominator 2500 for the back
Plan on cutting the A-arms and welding a cup in them

All I have bought is the 10" step notch so if I am going in the wrong direction, somebody please put me back on track before I spend my money