IMO any backspacing from 3 7/8th"- 4 1/4" is fine with 7" wide rims . Some aftermarket wheelmakers (Weld) do not offer a 7" rim with a 4" backspace . Therefore , a 7" rim with 4 1/2" backspace is needed and shims if necessary .
American Racing Wheels , ie "Torque Thrust" don't offer 4", 4.125 or 4.50 back spacing on their 7" wide rims. What they do offer is 3.76 which sort of puts an end to using them. Rocket and Vision do offer a 4.250 back space in their 7" wide rims. This is just a FYI for anyone hoping to run the Torque Thrust....