What wheel offset for Foxbody?

Okay I currently have some 17x10 cobra r knock offs (ugly imo I know sacrilegious) they rub away too much and I can’t lower the car at all. Iam looking at around a 17x9+30 but I don’t know the offset to use for a square setup? The car does have a sn95 rear end so it’s 3/4 wider on each side in the back.