Dart muffler configuration

Hi fellas.
I want to order a set of mufflers for the 340 Dart, but I dunno what the correct configuration of the inlet/outlet should be. I have been thinking the offset inlet and center outlet is what I need, but I don't know for sure. I am going to use a set of stock "over the axle" pipes, so the mufflers have to be the correct orientation in order for the pipes to line up correctly.
What did the factory mufflers have as far as inlet/outlet positions, and also muffler body length?

Thanks in advance.

George