The threaded tangs were only for the first batch made by Camillus shipped Feb 1943. That pommel is a "post-production modification" possibly after the original pommel snapped off.
Are you intending to re-use the pommel you took off or did you get a replacement pommel from Kabar? If you are wanting to replace the "old" pommel with a replacement flat pommel, I'd carefully cut down the tang tip to fit into the slot on the new pommel, necking it down to just fit into the slot with the pommel pin hole lining up with the hole in the tang. You can always cut off any excess tang sticking out through the slot. Your handle might end up being a tad shorter than "original" but it'll look just fine.