Re: OMC parts source?
BESIDES THE OBLIGITORY IBOATS SEARCH, I have found all that I needed on eBay, go2marine and crowley marine.
I too needed a thermostat housing, but just could not find one. I was going to get one for a 351W Mercruiser and make it work, but I ended up fabricating one on my own that matched my original ( I am a welder by trade ).
I also kept an eye on craigslist. I was lucky enough to spot an add for an electric shift leg, for $500, that was coming off an old Grady that was being scrapped. When I looked close at the picture, I recognized the 351w. Same year and model as mine. I called the guy and he said if I came and bought the leg, I could have the engine and int housing to boot. He even threw in 3 props for it. Now I have a spare EVERYTHING.
Good Luck