where does one find the engine number stamped on a 606.912 engine? it seems there are two different part numbers, and it depends on your engine number?

edit: also the photos of the new vacuum pump have a threaded fitting, and also a small barbed fitting. i looked at the one in my car, and it only has the threaded fitting. no barbed fitting. should i just put a rubber cap over the barbed fitting to close it off?

thanks