Don't hold me to this (because I don't have the same fenders as yours) but from what I've read around here, I think people generally get away with 245 section tires on stock offset wheels without significant modifications.
Your best bet might be to find someone on the forum with a similar car and copy their setup...Obviously, you will want to make sure you're looking at the same body style but you'll also want to pay attention to which rear axle they're running and their wheel offsets since these are important variables. Assuming you have all of that down, you'll still need to allow allow for the small variations from car to car that may require a rolled fender lip or a small spacer.
If you haven't done so already, go check which rear axle you have. Almost certainly, this will be a 7.25" but if you're not sure, count the bolts on the rear cover and get back to us.
If it IS a 7.25" consider sticking with stock width rubber since it will not live long with excessive traction anyway. Some may disagree with that but I know mine didn't hold up.