Slant Six Build Ideas

I have no experience with either brand of exhaust that you mentioned, but I have done lots of exhaust using pre bent pipes over the years in my work. Usually Walker or Maremont.
It was not at all uncommon for the tail pipe to be a size smaller than the extension pipe going into the inlet of the muffler.

The size of the exhaust is not it issue with Accurate it is the figment since they claim to use NOS parts to make their reproductions. They berated me saying that an unrestored car that has an original exhaust is wrong and that they are the basically the ultimate authority on exhausts. They can go f themselves.