GM A body wheel size upgrade

Hello,
I am in the process of installing a cpp pro touring kit w/ front coil overs, drop spindles and big brakes for my 72 Olds Cutlass. The issue I am having is with rim sizes and measurements. This is my first build, so I am trying to get everything right the first time. I am looking at 18" rims, but the ones I found that I like are 8.5" wide with offset of 35 and backspace of 6.13. Would this rim work, or is 8.5" to wide? Is the offset and backspace on this rim good, bad, ok? Any help would be greatly appreciated.

Thank you!

Good Afternoon,

The big brake kit is a Zero offset front and an 1/8" offset rear (per side) with this being said, a standard offset type wheel will fit on that car or what the wheel company recommends since the brakes dont move you out.

I just finished a '70 Buick GS A-body with 17x10.5" front and 17x12.5" rears, so I think 8.5" wheels are no problem. However, 6+ inches of backspace definitely is a problem. A wheel with about 4.75" backspace is about what you want. A 8.5" wheel (measured from bead to bead) has about 9.5" width measured from outer lip to lip. The inner lip is where the backspace measurement is taken from down to the rotor/drum mounting surface. A 9.5" lip to lip wheel with 4.75" backspace places the mounting surface exactly in the center of the wheel. This is called 0 offset. This is perfect for the rear. A wheel with slightly more backspace is ideal for the front-maybe 5". BTW, please don't try the 10.5"/12.5" wheels at home without adult supervision!
Paul