Stock Exhaust Question

I know this has probably been asked before but it seems like everyone is advertising exhaust systems that are 2¼", 2½" and 3". I have a 1968 Dodge Dart GTS, 383 with a 4-speed. What would the stock exhaust system have been?

Also, where is the best place to purchase the complete system from the stock exhaust manifolds back, including mufflers?

Thanks,
Al in Maine