Yup, you're right, they can fit with just a 7/8 or no spacer at all. They have to be 18" though. The IRS bolt isn't my problem, it is the inner knuckle that I would hit.
I thought about grinding it down, but the back of my car sees plenty of flex so I didn't want to sacrafice too much integrity back there.
Paul and Jon pulled the rear rubber bumpers off the top and bottom of my rear springs, which dropped it about 3/4 - 1" more in the back. When the back dropped, it pulled the wheels up and in more. They just sit right at the edge now, but not nearly as much as before. I rolled the wheel well lip a little to help give me a little more room, but since it is right at the edge, I don't think it will help much.