That boat was made to go fast (25+ knots).
Probably had Volvo gas motors that are probably not cost effective to repair.
So...I would guess after restoring/rebuilding the interior, you have a choice of:
Single diesel/outdrive (Volvo or Yanmar or
Twin gas/outdrive (Mercruiser)
Single gas/outdrive (Mercruiser)
Outboard/s

They used a lot of plywood encapsulated in polyester resin for building the transom and stringers, if the wood is wet or rotting it has to be removed and rebuilt. Foam boards are the best for stringers, and multiple layers of marine grade plywood laminated together for the transom.

Alot depends on if you want to go fast.
The hull was designed to go fast so it would be a nice to bring it back up to speed.
But if speed isn't important a 9.9 hp outboard would push that boat a ~ 6knts.