The cuda convertible project is hitting it's stride now, and it's time to pick out the wheels. It'll have an RMS susp. front and rear with 18x8 up front and 18x10 in the rear. I need advise on the back space on the 18x10 rear. No changes were made in the rear width or perch.

thanks,
oh, and the motor dyno'd at 790.

With an aftermarket rear suspension setup and everything else, I would say your best bet is to actually measure up your actual car and order the backspacing to what will fit the car best.

I found out here years ago not to trust the answer to this question,I asked the same but for a RR and was told that such and such rim would fit,guy went on and on,tires rubbed !
Might be better to just ask how to do your own measuring to get an exact fit instead of ending up wasting hundreds of dollars on rims that do not fit.

I run 9.5"x17" on the rear of a Challenger. 5.5" backspace with factory axle and spring location. The fender lip is trimmed a little. Ideal backspace in my application would probably be 5.25". If springs are moved in, you'd want a bit more backspace.

Before ordering the wheels I measured all four corners then borrowed a test wheel/tire from the dealer and measured again relative to the test wheel. I'd recommend you do the same as each chassis can vary.