That certainly is a new approach to fitting rubber. It seemed to be a bit intensive time wise and now with a custom backspace wheel, may not have been the cheapest, nor quickest, method to achive a bolt in fit, but I'm glad it worked for you.

The simpler bolt in method is to move the springs inboard 3/4 to 1 inch, then bolt in the B body rear. While the B body housing does not offer any more wheel well room than the E body housing, their ready availability does make it easier for most guys than cutting and rewelding the perches off the E body rear. However, either of these changes will alter the required backspace to fit the rims, especially since there is a difference in B body housing widths pre/post 67.

For my Challenger, the 3/4" spring move combined with a '67 B body housing allow a 15x10 with 5" backspace install that resulted in a 12" wide tire fitting with room to spare on both the spring and fender side. Entirely bolt in, using off the shelf parts.

BTW, the splayed spring design is a handling benefit that is designed in to all E bodies, post 72 B bodies, and all FJM bodies. E bodies are narrower at the front, while all other are narrower in the rear. What the splayed mount does is put the spring in a position that provides additional torsional resistance to the leaf, hence more roll resistance to the body, and minimizes roll steer by the rear housing moving and altering wheelbase length. The extra tread width doesn't contribute to either of these attributes.