Re: 12 HP Sea King Mod GG 00168 Fuel Pump
That model number can't be correct. Can I guess it is GG-9016B? That would be a 1956 with integral fuel tank, meaning the accessory fuel pump kit has been installed.
Anyhow, OMC stopped producing individual parts for those pumps around 40 years ago. The diaphragm number was 376619, if you think you can find one. Remember, it will be 40 some years old if you do.
Best thing you can do is buy a new fuel pump here at iboats. Part number 18-7351. You will have to re-route the hoses.