who's Running 18 "s ?

Yes, the brakes are stock, it's a 74, want to go to big 4-wheel disks, but first things first. As for wheel backspace, the front are 17 x 7 with a 4" backspace, and the back are 18 x 8 with a 4 1/2" backspace. The tires are Falken FK-452, 225-45ZR17 on the front, 245-40ZR18 on the back. They tuck very nicely.
I think that you can convert from the OEM drums to disks, several manufacturers make kits, but you would have to measure after installation to verify fitment. I used the wheelrite tool to check offset before ordering your wheels. If you are going to order these from Centerline, buy them direct, and look at all of the 2-piece designs, they sold me these for the same price as the cheapest 2-piece on the website, even though these are the most expensive of the style.
You can PM me if you have more questions about the car, wheels, tires, or any other questions you may have.