SIGNED mr norm tri-power air cleaner for hood tach

Not sure if this might help, but if he can't sell you one outright, he might be able to tell you where to look.

http://www.tachman.com/dixco.htm

http://www.tachman.com/index.htm

One other thing you might do. Set up a search on E-bay for Dixco Tachs. Even if it is for another brand, you might buy it right. (cheap) then, send it off to be restored/upgrades to your specs.