As a good operating practice , one should be very careful when changing something on vintage plane, remember these old ones operated for years and thousands of hours during the war and after, the folks at places like North American or Douglas or Rolls Royce were pretty smart and had a lot of money for planning and testing.
A T 6 took off from Mesa Az., promptly had engine failure and a crash and fire with two fatalities.
NTSB found that someone had monkeyed with the fuel system which was well proved in stock ones. Normal is 2 wing tanks with a small reserve in part of the left one. The fuel selector can be left or right or reserve or off. Someone had blanked of the reserve part of the tank and had a bogus fuel selector which would still allow it to be turned to the blanked off spot thus shutting off all flow. Such a small thing to loose two people and a nice plane over. It s possible the work was done by mechanic who didnt even make the pilot aware of the catch 22.