I'm on rock auto getting ready to order some more brake parts I'm getting the spring kit and wheel cylinders for my rear drums they have two different sizes for drums 9 and 10 inch. Without the obvious me going outside and taking my wheels off and measuring ( it's dark and cold out there) how can I tell what size mine are did they use certain size for certain years that kinda thing? Mine is a 75 dart with large bolt pattern front disks. The rear is a 7 1/4 thanks
