Rubbing issue with 20x8 255/35/20 rears

[OZ Duster]

After a number of checks to the rear suspension I believe the rubbing issues are the Wilwood disk brakes. The rear track has been increased by one inch over stock to 61" and has resulted in the rubbing on the guard lip. I can get a wheel I like in 17 x 8 with an ET of +15mm which will allow me to tuck the wheel up in the rear (compensating for the increased track). The Same wheel on the front will result in a ~ 5" back space, the current 18x8 ET 0 (4.5" backspace) appears to have ample clearance all round. Is this acceptable on a 1969 camaro with Wilwood disks?

spacers are illegal in Australia so that is out of the question before it is offered up. I see a lot of camaros on here with massive wheel size and width just need to know if the back space mentioned is suitable

Cheers