Have you test fit those front wheels yet? I've never been able to fit more than 4.75 backspace on the front of E and B bodies with a 15" wheel. They hit the upper ball joint.
Tubular upper arms can give more backspace clearance for 15" rims. The factory upper has a lip, whereas the tubular have a straight sleeve.
What you could do in the front is just add some steel circle track wheel spacers. They come in 1/4", 3/16" 1/8"....
You need to look at lower front corner fender clearance. You can push out that corner for more clearance by lengthening the lower fender brace. May have remove or loosen the lower valance for that. And then see if it will bolt back on after pushed back.
