I threw my planer head away (actually recycled at the scrap yard), and I kept the jointer head. I use it in my hydraulic press when I need to bend a curve into heavy gauge metal. I've seen a lot of folks try to sell them, with minimal success. The knives can usually be resold to someone who needs an extra set. It's one of those deals where if you can find the exact person who needs it, it's worth quite a lot...but they seem to be few and far between. Some folks who restore older tools sometimes buy them to have re machined to fit whatever they are rebuilding. It may depend on how much work you want to put into selling them, in my case I wasn't willing to work at too hard. You could also keep them, if you think you'll ever sell those machines; you might get more selling the old machine with the original head, and the spiral head separately.