78 250 case replacement

So my newly acquired 78 250cr wasnt running the best. It acted like timing was off( hard to start, often backfiring or firing through the exhaust) so I pulled the flywheel to find that 2 of the 3 holes for the ignition plate were rotted out and filled with epoxy. theres also a large glob of epoxy on the case wall of the crankcase under the crank bearing. Im guessing I going to need a different set of cases as Im afraid as I dig in more I will find more rot. So my question is, what years will work? Is it possible that cases from a 79 will work? wheres the best place to find them?

Yes 79 cases will work for you. 1980/81 cases have a different cylinder stud spacing and other changes so the 80/81 cases will not work. Watch Ebay for cases and ask lots of questions from the seller. Facebook market place also ask lots of questions.

Marty