So I have a 12 bolt that has been narrowed one inch from factory. My rear end measures 59" overall axle to axle. I may be wrong but everything I have read the factory 10 bolt 64 rear end was 60" end to end. The next modifications were to the inner fender well. Obviously I had to do it before paint because I cut the outer wheel housing about three quarters the way up and pushed it out toward the quarter. I then welded in some metal to join the well to the quarter. Then about 3/4" of the lip was trimmed away. Bear in mind I did this 20 years ago. I ran the car with a 28x10" slicks that were basically a 275/60/15's I think. My main thing back then was I didn't want to cut the car up (tub it) and I am glad I didn't. So here's a shot of the inner wheel well looking out toward the quarter. If you look closely you can see where the pieces were welded in. I think this mod gave me roughly another inch of play. I can roll a 20x10 with a 275/35/20 without touching anything and the car's frame resting on the axle without a bump stop.
