Thought that I might be able to edit my previous post and add this on but apparently not, the “mechanics” of this forum drive me nuts at times!
So this may be useful to you
https://www.dropbox.com/s/ttyz98h30996j4o/Tecumseh%20OH1400001.pdf
If you would like the parts list to go with it I will scan it and post it but there are another 20 pages!
A lot of US manufacturers used third party mufflers, many bearing the name Nelson.
https://www.nelsonglobalproducts.com/catalogs/
On my puter the above link is very slow to open but it does eventually!