BMatthews

Depends on the cylinder head setup. Many diesels of this type use a fin jacket that wraps up and over the head and has the contra piston threads in it. Very few use a separate head that screws in or down. So at the very least you'd need to make a new fin jacket that incorporates the internal head shape as well as the glow plug threading to take a regular plug. Or a fin jacket that has an open head to allow a Cox head to fit.

For the smaller sizes the hole for the element in a regular plug shape is large enough that it's hard to achieve a proper compression ratio.

So all in all yes it can be done but it would need some fairly major machine work. You couldn't just mod an existing head for them.