Leaf spring recommendations

225-60x15 on 8" tires easily fit those wheelwells. You might consider getting new wheels with more offset and sell the ones you have. Then you coukd keel the shocks. Obviously your 9" is wider than an A-body rear. Check the clearance between the rear springs and the inside of the tires. That will show you how much to change the offset.Try to center the tire in the wheel well.
Another thing is if you get the rear end higher with SS springs, you need to check your shock extension to make sure they don't extend to the limit and unload the tires. SS springs when done correctly cause the rear of the body to rise on launch.