From my experience the 6 cylinder cars came with 9" brakes, the 8 cylinder with 10". If your rear end has been "fix" by previous owner anything is possible. Your wheel cylinder replacement should look just like the one you removed.
Seems like you are new to the car, why not get what you need to replace the timing chain and water pump and bond with your car. You will learn a lot and you can fix your fuel pump problem while you're at it.