Yep. I looked at them on Summit. Cragar soft 8s are 5 for $379+shipping in an 17X9 backspaced 5". Custom backspaced they go up to $580+shipping.........but I don't see why the 5" backspacing would not be OK with a 17" wheel. What's the extra .5" going to hit?
Pro Comp Series 97 in a 17X9 are 5 for $450 with 4.5" backspacing. Local pick up. I think that might be a better deal.
I don't want to bag on your idea, but a 5" back spaced will look very strange on a cruiser. Those tires would be right up to the frame and inner fenders when stuffed and that narrow really will give you a POS center gravity.