Re: develop motor of my wellcraft nova 1974
OMC is the outdrive manufacturer, and also makes all the accessories that adapt the Ford long block engine to the outdrive.
In your case, OMC used a Ford engine, they also used Chevy and others engines.
Your best bet for information is to find the full model number of your engine and drive, and buy the OEM service manuals that covers your engine and drive. Don't waste your money on the aftermarket Clymer or Seloc manuals. The leave out much of the needed details on almost everything you really need.