Remove the valve cover and watch the valves for the #6 cylinder as you turn the crankshaft clockwise from the front. The last valve in line is the #6 exhaust valve. Watch it open (spring compressing) and closing again. Just as the exhaust valve closes, the next one in line will begin to open...
Align the oil pump drive with a long screwdriver, and drop the distributor into the hole so the rotor aligns with the #1 spark plug wire. Turn the distributor housing clockwise until the points close, then turn it CCW until the points just barely open. Lock the distributor housing down at that point, and the timing should be close enough to start the engine.
I'm working on memorizing this quote; this procedure works perfect.
I'll bite on the 'engine that would only run with one spark plug removed' as well...
Piston installed upside down? Somehow?
Brad