Fords been out of marine business for decades, I'm not an I/O owner but I dont remember Ford ever offering a Mercruiser stern outdrive. Maybe the did, but long ago.... makes parts sourcing problematic.
Current owner doesnt know history, can he prove he's ever run it?
They all used to run, but it was parked for a reason.
Its nearly 50yrs old, and likely to need more work then you expect.
You didnt mention a price, but I was serious, unless the trailer is towable as is and you can drop it in the water and run it as is, its the type of deal where the owner should pay you to haul it off. Even for free, its likely to be the most expensive boat you ever own after a likely complete rehab stem to stern AND a new motor & outdrive....
A Huge investment in time and money