I can,t see that spring settling very much as it is already stretched three inches more than it was designed to be to work correctly. Why not use an A spring as it would be only an inch out. JW
I used those mounts on my AV8 build, I used a hybrid AV8 rear spring from Millworks on a 36 rear axle. Your axle is is about 3/4" longer on each end I believe. My shackles are still flat with a body on the frame. Build is still in progress, so we will see. They do sell spacers to space those mounts out further, just remember, the more you space it out, the more leverage is on the axle flange. I may space mine out and weld them on as one piece later if my shackles don't sag a little when finished. Factory used fine thread bolts, so I'm using fine thread grade 8 bolts and hardware. Get some more weight on the chassis and go from there.