Missleman's tip there should probably get ya home. You'd be surprised how willing to help a lot of these manufacturer support teams are. I have an OS .10 engine that was my Father's. I new it was at least 20 to 30 yrs old & had no idea what model it was or how to go about finding an exhaust for it. The only thing it showed on the side of the engine case was: OS 10, no model numbers or letters to go by or anything. I emailed OS's customer service/support team & they had me send them a pic of the engine. The very next day they had identified it as a 1964 OS .10. I forget the model name now but the point is that it turned out to be over 40 yrs old & they were able to identify it as soon as they saw it! They were also able to give me the info I needed regarding the type of exhaust used for it back in the day. By the way, that engine still runs like a wild screaming banshee!!

So I'm sure if OS was able to find what I needed to know after 40 yrs, I'll bet Midwest can get you what you need too. Good luck in your new build!![sm=thumbup.gif][sm=thumbup.gif][sm=thumbup.gif]