I have knitted socks with a kit that I got from the Red Cross as a collectors item from WW2. It contained a pattern, yarn and needles for the period. The pattern was knitted from top down and easy instructions for turning a heal. The sock pattern made tall top socks for combat boots. The yarn was army green. The pattern did not have any instructions for replacing the heel. I did get some of the new yarns out there with nylon contained in it. It was yarn for making socks. I know I made several pairs and it was pricey. Good luck, I think I would darn the heel