That is one of the minor mysteries about the Atlas 10" and the early Craftsman 12". I tried to call Clausing this afternoon to see whether the 10D-38 or the L6-38 drawings would shed any light on the question. But they were closed for the holiday.
No one has ever come up with any parts lists earlier than the 10F except for the one on the 10E and it unfortunately doesn't have the lead screw and threading gears. Thanks to Sears Parts Direct several years ago, we do have parts lists on the 101.07360 through 101.07403 but they only hint at the answer. According to them, everything except the 07403 uses scroll 10D-38 and the 07403 uses L6-38. The parts lists for the 10F all say that it uses 10D-38. My suspicion is that when the 101.07403 came out, they had had complaints from customers about the staked-on half-nut actuating lever so the drilled and tapped a hole in the end of the shaft on the 10D-38 and called it L6-38. An unknown time later they must have decided to do the same thing on the 10F but instead of doing the logical thing and starting to use the L6-38, they added the tapped hole to the 10D-38 but failed to add an "A" to the part number. Or change the part number to 10F-38. Either one of which would have followed their system. Note that I also don't know what they did about the 10-29 Lever and the length of the square part of the shaft on the 10D-38.
Anyway, if the used 10D-38 on eBay has the hole drilled and tapped in the shaft, it should work fine. If it doesn't, drill and tap it #8-32 UNC. x 1/2" full threads. And if your old one was staked into the handle, you can use a #8 rack & panel washer and screw (AKA oval head screw).
