Interesting… I would have guessed they were all the same for the early style powerheads. I just grabbed my early powerhead and it is 11-spline. I don’t know what year it is, but it is ’52 or earlier judging by the water pump housing that is with it. The ’53 and ’54 share the same tower, so it is odd to me that they are different part numbers, but stranger things have happened. If you had reason to suspect it was from a ’54 QD, I’d say there is a strong likelihood you are correct. Below is a picture of the socket in the crankshaft of my powerhead just for a visual.
-Ben
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