can 85 (1st gen) RX7 front hubs be used?

Yup the front hubs and spindles are usable as well as the rear diff. The strut front end is modified like the Toyota struts to use with an upper control arm. Not a bad idea to use them in combination since the early RX7's have an unusual 4 bolt on 110mm bolt circle.

do you know of any websites that show this?

Heres a picture from the north american locost yahoo group files. It's identified as a Toyota spindle, but a Mazda one is nearly identical. It looks to be a Champion Motor Cars chassis, but I may be mistaken. (from http://photos.groups.yahoo.com/group/locost_north_america/vwp?.dir=/&.src=gr&.dnm=toyspndl.jpg&.view=t&.done=http%3a//photos.groups.ya hoo.com/group/locost_north_america/lst%3f%26.dir=/%26.src=gr%26.view=t) You may have to join the group to view anything, but most of the guys on there are quite helpful, so its not a problem.
Rescued attachment toyspndl.jpg