John, the sleeve I used is a Silver Seal MS229-1. Its the one Ted specified in one of his posts and is listed for the Y block on the Silver Seal web site. It measures 11/8". After pulling the damper and resetting it I can see that the front lip of the seal is just on the sleeve. The back lip is on by at least 3/16". I think I am good.
Thanks.

Mark

1956 Mercury M100
1955 Ford Fairlane Club Sedan
Delta, British Columbia