Re: 1957 johnson 18hp
Easy, place a free wanted ad on the aomci.org website. I became a member recently because those guys are both honest, helpful, know how to ship stuff, etc. You WILL get a response. If a member says they'll sell you one that has new coils, good lower unit, etc. then I'd be inclined to believe it and pay accordingly. I sold one for $600 that I'd fixed mechanically and put a decent paint job on. It was worth it. I'll bet you could get a good one that isn't freshly painted for half that or better. I've gotten mine on ebay but don't suggest it because they WILL get broken in shipping nearly every time.
Just a suggestion,
JBJ