Advice, please: too old to fly?

There can be no better source of advice than this group for my question: am
I too old to take up flying--and building an airplane?

Full disclosure. As a young man in the Korean War I was an aviation
machinist's mate in the Navy. As a forestry student in the late '50's I was
a smokejumper, so I have quite a bit of experience in the ultimate maneuver:
abandoning an airplane in flight. As a forester in Southeast Alaska, I had
many hours of time flying with a bush pilot, as a passenger. Lots of
airplanes in my background, but I'm now 73.

I find the Zenith STOL's irresistible. The 701, the 2-seater, can be flown
with a 10-hour sport license, so at my age--and limited time out there
ahead--it might make sense to focus on that airplane. But I'd really prefer
the 801, the 4-place plane. It would take longer to get the necessary
private pilot's license--40 hours of flying time instead of 10--but I see
that as a huge advantage: nothing beats experience. And flight training and
airplane building could proceed simultaneously, couldn't they?

I've enjoyed a great deal following the discussions on this board, and I've
learned a lot here. Maybe it has been the stimulus for my cockamamie dream.

Your knowledgeable comments will be most appreciated, and thanks a million.

Dick Behan