8" Backspacing w/ 18X10.5 rears on 2nd Gen?

[Raptor Pilot]

I am going install a C4 IRS on my '70 Formula and want to know if anybody can tell me off the top of their head if an 18X10.5 rear wheel will work with an 8" backspacing on that setup. I know that it wouldn't work on a standard 2nd gen rear susp., but I am thinking it might with the IRS. I do not have the parts available here to do a mock up/measurement right now however. I wouldn't be against mini-tubbing if necessary, but am also wondering if I'd be able to get the wheel flush with the quarter panel as much as I'd like.

Any opinions are welcome. This is, of course, based on a used set of wheels that I have an opportunity to get, or I'd simply order the BS that I need for the wheels and just go 18X10 instead.

[MrQuick]

If you can get the rims for real cheap go ahead and buy them. If they don't fit then you can sell them.
As far as fitting them on your bird and IRS for me would be a crap shoot. Your going to have to measure the full set up.
For a measurement im running 18x12's with a 8 3/8" bs on a stock rear end and is it sits so I can lower it below the rim line. I seem to remember that the Vette IRS is abit longer than a stock stick rear.