Re: '56 Johnson
Exactly what I was going to say. Try aomci.org and post a blurb in their classifieds and ask for a swap or cash. You'll never know what folks want to trade for until you try and the folks on aomci appreciate the old engines a lot more... in fact, a '56 is pretty new for them!
Oh, and an fyi, I recently got a '56 30hp and a '57 35hp for $100 where I live (Canada). The guy said the '57 ran and he did not know about the '56 (which was partially disassembled) but both seemed to have good compression via the pull start.