Tire size with DrDiff 1" offset spring mounts

Ebody Barracuda. 275/60 dot drag radials fit easy without the offset stuff. Least clearance is the sidewalk to spring behind the axle. What tires have you been able to fit with the offset springs? Does this kit move both the front and back of the spring 1" or is the shackel offset more than the front bracket to bring the springs closer to being parallel?

For reference

With the offset spring kit, a '68 B body axle housing, 1/2" front perch spacers, and custom backspace 10" rims: 295/65-15s fit fine on my '70 Cuda.

Dr Diff 1" relo on E-body rear end, 9" rims with 6" backspace, 275/40/18

I squeezed in a set of 325/50-15 Nitto's.
on 10 inch rims with 4 1/2" backspacing and a 1/4" thick steel spacer. It has a '68 B-Body Dana 60 with Dr Diff's inset hanger kit. I did have to massage the upper fender-well lip slightly.