The only thing I can say for sure is that the 1961 parts catalog confirms that the fuel pump pictured above is indeed correct for a 1961. Wish I could tell you how many years beyond 1961 that this particular pump applied, but I can't, although I would be curious to find out.
As far as how many are left, who knows, right? On the one hand I have been pleasantly surprised by how many so-called unobtanium parts I have been able to track down over the last year, yet on the other hand there are still a few parts that may elude my grasp forever. Again, who knows!