Here are shots of my '74 550 with a new OEM 4into4 exhaust installed. Now basically restored to full stock. Exceptions: cushioned Italian grips, removed the front disc hood, installed Hondaman electronic hybrid ignition unit. And that's all I can think of.
The Mac 4-1 system I had on previously is now on it's way across the ocean to Frostboy in the land down under, who has promised to give it a good home on his '76 550F. Nice.