I'm not sure if some of the same issues could come up on the T30 you are looking at. My T27 is 10 years older then yours at 1977.
With the T27 issues come up with the chain plates as they were glassed into knee walls and the wood core can/will rot. Also, cored decks can become soft or spongy.
Our A4 is 10 years older then the one you are interested in and still running well. Maintenance on the engine is pretty easy and there is a great support group at: Moyer Marine Atomic 4 Community - Powered by vBulletin
Sure, gasoline is more volatile then diesel but just using common sense and your nose helps. Run the engine compartment blower and sniff for fumes before you crank it. Diesel exhaust does not smell any better then gas and gasoline is a tad cheaper at the moment.