Petcock rebuilds = wasted money. Been there, done that, too many times, and no matter how careful or meticulous you are they just don't last that long.
Just fit a new $90 OEM petcock and the overflow tubes.
That way you can forget about the petcock for 10+ years, and when it does fail, the gas will pour onto the floor rather than into the cylinders.
+1 AND their is another huge benefit when buying a new OEM petcock. You also get a brand new fuel filter that is integrated into the petcock. Those mesh screens / filters get distorted and fail after a period of time and need to be replaced. When that filter fails debris then gets past the petcock and into the floats/needles of the carbs and leaks will occur.