Hi Will,
I assume to mean the rubber bung things that plug into the holes in the gusset plate at the front of the frame. (See photo, it's the rear one)
Failing that I guess you mean the rubber strip (see the other photo) that sits under the tank (there should be two of them)
The rubber strips sit wherever you want, one at the front and one at the back of the tank, you should be able to see the witness marks on the frame top tube where they used to sit.
I hope this helps
Webby
PS: The photos are of my 72 so it should be the same