If it is the same as '68 on F series, it should be easy to find in a salvage yard. I think '61 on is the same but not sure. Mine's had a '68 axle in it since I've owned it. I know the T mounts in the same fashion but '61 uses a separate fitting whereas the later fitting and hose is a unit that cannot be separated.
When I cleaned my vent, I found that it was only a small hole, probably less than 1/16". No idea if that is correct or if any filter material has rotted out since new, though.
Lawrenceville, GA