The only operational component on my 66 "A" code hardtop's engine that is not an original Ford item is the Pertronix ignition. I have a lot of confidence in the mechanical fuel pump, the venturi based carburetor, the alternator with diodes and the nut behind the wheel. Back when I worked for a living, I was in reliability. That job can be summed up in an easy term - "mean time between failures". We applied the principals of that term to off road racing and came to the final conclusion that the weakest link in an off road car, the item most likely to fail, was the electronic ignition. The next item was the clutch.
Jim