I have found a source for these pre chambers, finally. I have searched for months. Check out tractorhouse.com as of two days ago they had these pre chambers in stock. they are over size and they tell me the head needs to be machined out to take the new chambers. They also tell me that these are for the 1910 three cylinder and not from some other head that can be made to fit. an exact size will not stay in place for some reason, I guess because of the age of the heads. Let me know if this is the correct name of the supply house for these chambers or not as I am not at work where I have the info and I could have it wrong. They have almost everythiung I could not find at the more famous and bigger supply places. Thank god. LOL