Stock wheels with 12.50s

I have a set of 15x8 stock five spoke aluminum wheels with 33 x 12.50s on them I'd like to use on my 87 XJ but they touch the leaf spring, I have the same wheels with 32 x 11.50s on there now and they fit fine. How much of a wheel spacer would I need to clear safely? Thanks for any help.

Dont forget about the front when turning,based on the normal backspace used with 12.5's your looking at about a 1" spacer.

I'd say about a 1-1.75" spacer,
But even after that you might still rub on the front control arms.