TOPIC: 1956 Mark 55 short shaft

Since I don't know outboard pricing. There is a 1956 Mark 55 electric start on E-bay right now with controls. The motor lower unit is disassembled from the motor. but it's with it. The starting price is 400 dollars. Is that reasonable, in line with the market, or overpriced ? I have a 15 ft boat that I think would be a good fit for a 40 horse ?
Since I'll need a motor eventually ? I'm starting to look for a motor so I'm watching prices to get a good idea what to expect to pay ?
Opinions please, on both pricing and HP for a 15 footer

That is a bit overpriced for a basket case. If it was a complete unmolested engine than maybe, but there are a lot of red flags there. More like $150 to 200 bones for that one, methinks. Power wise it is a little light for a 15 footer, but propped right it won't be too bad. A lot depends on how engine friendly the hull is, some are just dogs no matter what you stick on them.