Hi.  Looks the same as the motor mount on my FS4798, dated 1992.  A stainless steel bracket with a triangular piece at the bottom slides into the bottom pocket, then is secured by two brass bolts (with wing nuts) at the top.
The stainless steel bracket provides a stand-off for a thick (abt 1.5") wooden board (made of 2 thinner boards), which is mounted so that it sits about 8" behind the transom.  A standard small outboard motor (I have a 2HP Yamaha, same vintage) then clamps onto that board.

From the difference in dates between your boat and mine, Flying Scot must have used this arrangement for at least the decade of the 80s -- probably longer.   So I think that if you contact Flying Scot Inc they would recognize it, and perhaps can still deliver a motor bracket that will fit.

Came back to this page -- realized the pictures in previous append were not visible. Should be fixed now.