To the best of my recollection the 3 pulley pump were the same pump as the earlier M38A1s, just the pulley was different. There was a modification on the early ones to put the bypass hose nipple onto them...can't remember if that was for the civilian pumps or the military.
I say they were the same because at one point the military bought a bunch of 2 pulley pumps and our BML machine shop in Winnipeg was tasked with making the 3 groove pulleys to replace the two groove.
I do have a NOS CDN2/CDN3 pump sitting on the shelf, but it isn't going anywhere.
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