Normally I would defer to Bondo's brain on this sorta' thing - but that '65 Deluxe is too weird/cool of a boat to let it go. You've got some sentimental value with it and I'm kinda' sappy too ... so, if it were me I would probably consider keeping it.
Here's the disclaimer: a restore/rebuild is going to be a process of tossing good money into something that nearly nobody else is gonna' want later. It's possibly/probably not going to be cheap - so determine how far you're willing to go on this financially and adjust accordingly (back to Bondo's plan if need be).
Assess your transom. If it was rebuilt well to support the OB, you may have just a limited amount of work to rebuild for an I/O. BUT LOOK CAREFULLY, some boats that had floor mounted Stringer Drives didn't have reinforced transoms and you don't wanna' clamp anything new to the back of that boat (even an OB really) without knowing it was built properly. After that, I would abandon the idea of refitting the boat with an old OMC. I have the Electric Shift Stringer, and while there are some things that I really like about it I don't recommend intentionally refitting to that drive. Look at refitting to a Mercruiser. If you have to do (or have already done) the transom work, then I would go straight to Mercruiser (the build it different for Merc vs. OMC).
It's likely a big, expensive project, but it is a cool old boat (If I run across one or an old Surfer, I'll have a hard time passing it by).
Welcome aboard.
