I have 1" wheel spacers and they work just fine with my Bullitts. I have to take the spacers off to put on the 16" wheels w/ drag radials as there is not enough of a hole on the wheel for the factory studs to sit in.
The factory wheels usually have these recessed holes in between the mounting holes that allow the stud to protrude through when using spacers. The problem with spacers usually lies with some aftermarket wheels that have a flat mounting surface without any recessed holes between the stud holes. Of course we're only talking for hubcentric spacers that bolt-on using the stock studs.
I am using 1 1/2 inch spacers and the stock studs do not protrude through the spacers. The wheels are nearly flush with the rear quarters just about perfect with my stock cobra wheels.