I’ve seen a few posts about people using these master cylinders, and I was able to get my hands on one pretty cheap.
From what I can tell the stock primary is 9/16-18 and the primary on the 1858 is 7/16- 24. So I would need a reducer with female 9/16 to make 7/16 to fit into the new MC. I’ve found plenty going the other way, but does anybody have a link to where I can find this adapter?

Thanks