Write to Mark Aksamit - he used to arrange SOHC/4 rides out of the Phoenix area every year. He owns (I think) Southwest Corvair (southwestcorvair.com - though I can't get the site to load this evening) and dealt in SOHC/4 parts for a while. I'm not sure if he still sells parts, but he should definitely have some good information on the Phoenix SOHC/4 scene.
The two email addresses I can find for him:
southwestcorvair@cox.net
MAksamit@ntwrld.com
--Glenn