Early a exahust suggestions?

Check TTI's web-site. If you send your cross-member they will notch the right side and re-weld a bottom plate for $100. However, offer is only if you buy their ~$800 headers. Maybe you can beg them to do it for $150 without a purchase.

However, I attach a schematic someone posted that shows a Hi-Po with a single factory exhaust. Interesting, because others show that the way to tell an original Hi-Po is by dual humps in the rear sheet metal. Maybe varied by year or Darts, Valiants, Barracudas. Looks like a single exhaust could be historic for some, though you went 360 anyway.