I went flush with the floor support that sits on top of the frame.

I used 1 full set of tubs welding them to the 1/2 tubs in the bed.

here is a pic that you can see the floor support and where I cut it. this makes it in past the spring flush with the frame.

I used a shackle flip and floped the A-body 8 3/4 on top of spring with same wheel/tire combo.

IIRC,Max just floped the 8 3/4 on top of the springs and used pre-made wheel tubbs.

***FYI*** the A-body 8 3/4 needs the large brake offset axles with 5 on 4.5 wbp. this make the whole 8 3/4 wider by 1/2" = 1/4" each side. so it tucks the 12" rim with a 4.5 backset on rims running a M/T 29x15x15 tire in the fenders.

if running a skinny 1 3/4" brake A-body axle you need a rim with 4 1/4" BS( best measure tire bulge/leaf spring clearance )