The part number for the implement shaft for 47 Quick Hitch snow blower for 4-5 series is BM20871 (It's cheaper buying the kit verses just buying the shaft alone dealer told me - comes with upstop bracket and some hardware and manuals) I can attest to the square version shaft fitting the snow blower fine as the half of shaft on the unit originally was the splined version. The splined version is to long from all I've been told, I was just gonna cut it down for it to work - but dealer made a deal with me on the correct shaft kit since they couldn't find the other half.
I do see that the BM kit is cheaper. Deere loves to offer kits cheaper then individual parts for some reason. Comparing the two mentioned shafts, there is a .04" difference in length. While the AM132904 shaft shows square in the parts books, the specs say it is a 15 spline. Not sure what that is about.