Rear tranny seal part # please?

G'day All,

I have a USA built (Ca) 1963 Plymouth Valiant (not the Aussie built cars) and it seems that the rear tranny seal is leaking badly.
It is the push button 904, of course.

Could someone please post a part # for the seal, so that I can source one from over there please ??

I have developed a consistant vibration which I am sure is the tailshaft (driveshaft?) and I am guessing that it has chewed up my rear tranny seal.
I will remove the tail shaft and have it checked, but I would like to get a seal in the meantime.

As always any help appreciated - many thanks in advance
Gary