Help with wheels after disc conversion

[macdaddy70]

I have done searches and cant find what I am looking for. 1970 LWB GMC with original 15" wheels. Recently had all new MOOG suspension and CPP disc brakes/booster/mc/prop valve installed.
Wheels are in place, but had to add washers to clear calipers. Backspace of original wheel is about 3 7/8". Approx 1/2 inch of washers had to be added for clearance. Does that mean that I need to look for a wheel with roughly 4.5" backspace?
I wanted to stay with stock look, but going to aftermarket aluminum, dont want to use a spacer.
Pics meant to show space from rotor to back of rim and clearance from caliper to inside of rim.