I used a 3/4 billet spacer on mine with an A-body 8.75 rear end. it cleared fine but there was more clearance on the outside of tire than the inside. With the later b-body rear the tires are almost perfectly centered, no spacers. I sold the spacers to my friend for his valiant build (the blue one), he's running an 8 1/4 rear end and the clearance between tire and springs is mighty close. Pretty sure the 8 1/4 rear end is a tad narrower than the 8.75.
pics are of my car using spacers, and my buddy's valiant build.