'79 was a great year! (Our boat was made that year, Tangerine Dream released Force Majeure, and I graduated from high school...) A 40-year old boat is going to be a bit tired. But it sounds like the one you found has been loved unconditionally.
My advice is to not get too caught up in the potential minutia of the survey. Major structural items notwithstanding! Our's had soft spots in the foredeck (delamination that we were well aware of) and the surveyor "sounded the alarms" on it, even suggesting we could potentially renegotiate the price. When I explained that the price was not going to be lower (both parties had already discussed it, and the price was already at the seller's rock bottom) he confided that it wasn't structural, and it was not going to sink the boat. But he was just doing his job as the buyer's surveyor.
Which leads me to my only other piece of advice (even though this is probably not your first rodeo), and that is be sure to hire your surveyor yourself, not one picked by the seller or his broker. Even though surveyors are impartial and objective, I've used both, and I'VE always felt more confident knowing he was working for ME.