Clean the carb, don't try to convert it to EFI. The small block and 280 is a solid combination, DP lower units can be had on ebay.
Looks like a fun project, but pick your battles. I wouldn't refinish the deck until you replace the fuel tank.
Ryan (RPTPL) would be a good person to talk to, he recently re-did his 17' Radon, and it came out beautiful.
Pros and cons to every boat/hull/condition. Just stick to a budget. People wait years to find their perfect boat.
These guys lower the price about every other day (starting ask was 48, now at 30 10 days later). In a few more weeks, it may be worth considering. Yank the old I/O and slap a big OB on the back. These 17x8's...