What you have to be careful of is exceeding the clamping force of your wheel studs. My roadster had been run for years before I got it with 1" wheel spacers and 1/2" studs. Light car and only running 6.40s-6.60s in the 1/8th.
I didn't feel comfortable with that setup so I got new wheels that didn't need the spacer. The problem to me is figuring out how much clamping force you have to have with the weight of your car, size of your tire and torque on the rearend, relating to the spacer and wheel stud involved.
Curtis