widest tire with spring relocation

I'm in the process of doing the same thing. One thing that was pointed out is by going to a larger dia wheel you can get better rubber. I'm going with 17s 8 front 9 rear.
Pretty sure it will require "adjustments", also relocating springs in 3/4" (1/2") respectively.

Don't want to do the 3" relocation because this is a road car, it needs to have the best handling I can get and don't want to mess with spring rates.

My comment is only directed at tire choices, I want modern sticky rubber. YMMV