Thankyou! If I were you, I'd set your 9" rear up w/ the '68-'70 B body dimensions and use the Dr. Diff offset spring hanger kit to use a 15x10 rim. His kit allows you to bolt in a B body rear and fit a 10" wheel pretty easy.

Mine is a stock width E body rear w/ stock front spring location, but I use the .850" offset rear shackles to get some added clearance and to make the springs closer to parallel. They're wider at the rear in the stock configuration.
I use 15x8.5" wheels w/ 5" of backspacing and run both 295-65 radials or 29.5x10.5 slicks on it.
Just trimmed the inside of the wheelwell lip to clear the tires.

Here's a pic w/ the slicks on it.