Tire Size help

I'm needing to choose a rear gear ratio for my '69 Barracuda and so was needing to pick a rear tire size. I'm looking for the widest tire I can fit comfortably. I will be going with a 17" wheel and I have a spring relocation kit on it. Rear discs on an 8 & 3/4. Don't like the rubber band look so I'm wanting some sidewall. I will determine back spacing later but was wondering if anybody has this setup or had any experience with this situation. Pics would be helpful. Thanks.