What to tell the exhaust shop.

Thank you, I appreciate your input before I get this done. I was thinking that an early A body car like mine 64 Dart GT may not have enough clearance in the engine compartment for 2.5 inch pipes. My car is manual everything no power steering, or air conditioning. Has anyone else installed 2.5 inch pipe in the engine bay in a car similar to mine?
I have 2.5" from stock manifold through a Flowmaster all the way back. Awesome sound even with 1bbl