If you really want to get the ’57 Fastwin up and running again, any OMC 18/20/25 horse powerhead thru 1976 should bolt right on to the ’57 exhaust housing. The only problem might be the driveshaft spline count and mounting the hood as the ’59 and later models were thermostat temperature controlled and don’t have the mounts on the cylinder head needed to mount the ’57 hood. Heck, running it without the hood and lower pans on would look cool and qualify it as a rat motor!
