1969 Dart---Spring relocation with mini-tubs

Just trying to get a second and maybe a third opinion, along with some free knowledge:

Trying to get a little more tire at the rear of a 1969 Dart, stroked 416, with an 8 3/4 and currently with stock springs.

Plan is to relocate the springs to the frame rails and mini-tub the car. I'm being told this will allow for about 12" wide tires...but I have seen threads that say you can get the 12" wide tires at the rear with just the spring location and no tubbing. Looking for confirmation and/or any recommendations on most economical and (more importantly) best options.

Based on the current plan, I believe I would need:
(2) Upper rear shackle bolt sleeves (to be welded into chassis frame rail) that would include (4) bushings for the (2) upper shackle bolts
(2) super stock springs with bushings if/where needed for installation
(2) "special" shackle assemblies (as needed) to insure correct fits and no problems

Any suggestions are welcome and appreciated...including suppliers and contact information for the above listed parts or other parts the forum finds I may have overlooked.

Thanks