My suggestion then would be to figure out which Wilwood kit that you have, and the actual width of the rear axle. There are several Wilwood kits out there, and depending on the kit they're based on different spindles which changes the track width up front.
In the back, you can measure from the wheel mounting surface on the drum back to the leaf spring, as that will give us a good idea of the backspace needed. Although we'd still need to know if the leaf springs are in the stock location, relocated 3" under the frame rails, or even a 1/2" offset at the hanger/shackle.
Without that info and considering you definitely have aftermarket parts that don't necessarily match and factory specs we'd just be guessing. The Wilwood kit could be for drum or disk spindles which changes the track a lot, the rear end may be narrowed, the springs could be moved, etc.