I wrote an article for The Gas Engine Magazine Sept./Oct. 1984, about the restoration of 2 IHC M engines (1927 and '28). You can either get a back issue from GEM or view it on line. The article was named 'A tale of 2 engines. I included pictures which may help you identify parts. have a look at H&M Enterprises IHC M parts list too - he has a diagram on the page. H&M is a sponsor here on the Stak - look on the sponsors page for his site.
I may even go ahead and braze up the crack in the cam cover. One of the arms that run off the cam was brazed either decades ago by dad, or a half century ago by my great grandfather.and just some words of encouragement, i have brought worse back to life (of that same engine), you can do it!