Zaptel 32 bit make on 64 bit intel linux

This is a more specific question from another item I opened ( … ght=zaptel)

Is it even possible to create a 32 bit version of the Zaptel code on a 64 bit system? What version of the kernel source should I link to from /usr/src/linux ? Can I really generate 32 bit device drivers then run them on a 64 bit kernel? Thanks - sorry if the questions are a bit basic.