Yeah, gen I a more of a challenge in the rear. Though I never understood what the issue is up front. The one time I looked at a gen I up front, it seemed to look pretty much like a gen II. I'm curious what the difference is and where exactly you are seeing the rubbing.
Wrt to the rear, the following advice, which will work on a gen II, may be of help to you:
I have 235 series tires on 8.5" rims with a 44.5mm offset AND I have 20mm spacers on the rear. This is on a gen II.
Initially I had rubbing even after removing all of the fender lip.
Turned out I hadn't removed that part of the fender lip located just behind the rear door and which overlaps with the molding. I had also tappered the lip, as it is coming down from the top, so that I had a graceful mating to the molding. Well, I redid this whole molding section...basically removed the molding part of the lip too. I had to relocate the little nut the holds the molding in place on the lip down by, I would say, ~4" or so. That did the trick.
It sort of always annoyed me that Ford didn't center the rear wheel in the wheel well. Why did they push it forwards? It looks like a half-done job.
FWIW.
Michael