I got 1.5" and 2" spacers to play with the backspacing with different wheel and tire sets. 15" wheels will hit my TROs. deep offset 17" will have contact (radius arm bolt to tire) at full turn.
I need to keep tire thread under flare to pass our local vehicle safety inspection.
Looks like 1" thick spacers will work with the 15" slotted mag wheels that I have. I have the 1.5" spacers on now but front tires sticks out a little too much (legally).