If I remember correctly there was one disc in my Hupp clutch that went in by itself. That really does not answer your question though , sorry . Looks like a Hyatt roller bearing, I've had very good luck consulting with a bearing specialty company. Are you quite sure it needs replacing? I must confess not an expert , but went thru some problems with my multiple disc clutch, kind of a no-man's land, just tryin' to help a bit. A real bummer not much info in that book.Have you tried any antique truck forums? Ken