wheel backspacing

I have a 55 Bel Air and I have installed the rear pocket spring kit from Ecklers which moves the rear springs in and under the frame. I have also installed the front disk kit which I think moved the front wheels out about an inch each side.

I have 15 inches clearance inside the rear fender wells and have been told that 17 x 9 1/2 with 5 1/2 backspace will work. I would like to go to 6 1/2 backspace instead. We all know how hard it is to change the rear wheels on these.

I have no idea about the front but would like to run 17 x 8 with around 4 backspace.

How do these numbers sound?

Heres some links that might help ya figure it out...
http://www.rsracing.com/tech-wheel.html
http://www.centerlinewheels.com/faq.php
http://chevyhiperformance.com/techarticles/92318/
http://www.yokohamatire.com/utcustom.asp [