Our Tubes Fit 24.5" to 28" diameter slicks with 8.0" to 10.5" tread width. So this will definitely have no problem fitting your 8in wide wheel.
If you have questions regarding the install, Our Mustang Experts are here Monday-Friday from 9AM-9PM EST and Saturdays from 9AM-5:30PM EST. If you want to hit them up, their number is 866.727.1266. I can also have one of them call you directly. As far as the discount code goes, Shoot me a PM & I'll hook you up with the code.
Let me know if you have any questions or need further assistance.