(scratches head) . . .
Forgive me for sounding stupid, but isn't this a Holden fuel/vacuum pump, the second type with double-acting vacuum section? It's even got the forged arm of the right shape for a grey motor. OK, so it's made in England, but I thought quite a few Holden fuel pumps were.
The small-block Chev V8 fuel pumps, to the best of my knowledge, were serviced only as an assembly (so when they died, into the bin, and no repair kit), didn't have a glass bowl, and were mounted on the block upside-down compared with the Holden fuel pumps - that is, the rocker arm and link are on the top side of the diaphragm, and the fuel connections and valves are on the bottom side of the diaphragm. I don't know whether any of the 1950s Chevrolet V8 cars even had vacuum wipers.
You might take a look at
http://www.chevsofthe40s.com in the "fuel" section. They are selling new fuel/vacuum pumps identical in appearance to this one, to suit the stovebolt 6-cylinder motor. You'd only have to change the rocker arm for a Holden one, but that's slightly off-topic.
Rob