.....I've read about the backspacing available on the Gen III's on 'camaroz28.com'. So a search there will give you your answer. I don't know if this is any help or not, but I once had an
'84 Z-28 with 3 1/2" backspaced wheels on it {Center Line Convo Pro wheels}. But this was WAY to long ago for me to remember if more backspacing would have worked or not..... Bill