66 ss wheel/tire question...PB Pro-touring dropmember

[66C06]

Hey folks, I have a 66 step that I will be doing a pro-touring frame off restomod to and I had a couple of questions...

First a little bit of insight to the planned build:

-frame off resto
-Porterbuilt pro-touring front/rear coilover DM
-C6 ZO6 brakes all around (looking at boris' kit)
-Either a wet sump LS7 or 427 LS3 Stroker
-TCI 6x 6 speed (modded 4L80e) with electronic paddle shifters (when not using the paddles it works as a regular 4spd auto controlled on the column shifter).
-Moser built rear end (true-trac, 3.73's, 33 spline

What I am trying to do is mimic the paint scheme of my ZO6. I found that if I use the ZO6 brakes and stay with the corvette bolt pattern I can use the same wheels that I have on my vette. They come in sizes from 18-20" and range from 9.5 to 12" width. I am having trouble trying to decipher which wheels will fit under the step side stock fender with out doing a mini tub. They offer a big range of offsets which is great. Ideally I would like to do a 20x12 on the rear and 20x9.5 on the front. What size tire would I have to run to fit a 12" wide wheel? I would like to have as much sidewall as I can fit. If worse comes to worse I can run a 20x10 rear and front if necessary. Here is a link to the wheel specs (they will be the deep concave): http://www.forgestar.com/v2/wheelscf5.php

See wheels on vette below: 19x10 front 19x12 rear