Re: 1962 custom craft resto
It's not easy. Many sellers will have NO idea what length shaft their OB is.
I 'decided' I'd like to have a 65hp Merc on my 1960 Glastron FireFlite, which has a short transom. Short shaft Merc 65hp, 650's are fairly uncommon w/ in 300+miles of me, I possibly missed 1 or 2 in over 2yrs of looking. Other places they may be more prevalent. So I spent some time & found an Evinrude 75hp motor that is a similar vintage to the boat & is a short shaft OB.
Since you don't currently have an OB, it isn't too soon to be looking. Pick a hp range you'd like to find, start looking and put the word out. Looking for an OB will lead you to buy junk boats, w/ or w/out trailers, but have a good rebuild candidate OB.
Decide if you'd rather get a vintage motor that 'matches' the boat or a more modern motor that might have tilt & trim. You can get LOTS of parts for Johnson & Evinrude OB's at NAPA stores, possibly some Mercury parts. The newer the motor, the easier it should be to locate parts. Iboats carries OB service parts as does other online vendors.
If you want to get an old Merc & get it running, it is possible, but may be much more difficult then a similar age Johnson.
good luck