Aircraft Engine Spark Plugs

Can anyone offer me advice on aircraft engine spark plugs, please?

During my garage clearout (see More mystery instrument panels thread), I have found examples of the following types:

Champion C26S (a quick Google shows them as listed for the Warner SS50 and SS50A seven cylinder radial engines, the Lycoming O-340 and Continental A100-1 & A100-2)

Champion R33S (Pratt and Whitney Double Wasp)

All appear to be in either NOS or overhauled condition and they are protected by cardboard sleeves or natty aluminium “flasks”.

Is there any point in me trying to sell them or is the world awash with spark plugs, making them worthless? I’ve taken an odd one to aerojumbles, but there has never been a flicker of interest. And I could put the space taken up in the garage to better use.

Thanks in advance!