Interesting but rather mixed up post. Buying a spare timing gear set in 1959 would have meant it was for a B16. Not the same as for the B18/20. When a B16 gear goes out the engine just stops with no damage. Having had one fail back in 1967 I didn't instantly realise the gear had gone, thought it was electrical but that showed that the dizzy wasn't rotating which meant a gear failure. My gear had the fibre gear molded to the a centre which just had a coarse knurling on it. Maybe, later replacement gears have a star shaped steel centre the same as the B18/20 fibre gears. At least they will allow the engine to noisily carry on running when they fail, even to the extent of just falling off when you take off the timing cover.