rear leaf spring recommendations..??????
I have a 67 cuda that I had to use the offset hangers and shackles to get that exact same tire and wheel you have under the car. Not the hangers and shackles that relocates the hangers to the frame rail but the others that require no welding except on the perches. You can get them at Summit. Before I had 1/2" between the leaf and the small 14" tire.
Here are some pics with the 275/60/15 after the offset hanger and shackle installation.
I don't know if this helps any but just a option you can use to make sure you have plenty of room if you are going to be changing out the leafs anyway.
I would make sure the leafs are the same number on each side of the car..... your on the right track.
