In my scrap box I have a muffler to fit your J.
The indicated holes have been over sized but
you have the ability to plug and re-tap them.
Its fine other than that. It’s junk to me. Its
yours if you want it. I can’t help with the
turn out that goes on the end.
Tubs.
A "Boathouse Repair" is one thats done without having tools or the skills to do it properly.