As I remember, the wheel opening on a 66 Coronet does not allow much tire, unless the outer body and outer wheel housing are opened up, or the rear end is lifted pretty high. I believe the 70 series tires I ran on my Coronet rubbed on both the inside and the outside wheel tub. The 66 & 67 Coronet bodies were not very tire friendly. The 65's were better, and the 68s were much improved, but the 66 & 67 not so much. Might want yo look into that if your thinking a lot of power. Gene