Thank you to everyone that replied.
I found two mufflers that were almost direct replacements. Donaldson M120225 and Nelson 86147M. They both had the exact dimensions. I decided to go with Nelson because it was about half the cost of the Donaldson. I ordered it on 05/17/2023 through Truck Pipe USA, Ocala, FL, and had it shipped directly to Cummins in Clinton Twp., MI, where the coach is for repairs. According to the tracking information, it should be at Cummins today. Once installed, I’ll comment on the noise factor.
