I'm trying to figure out what type of tires I should be looking at for my Miata and I'm having a hard time understanding what rules will be applied.  

It starts with Hoosier's announcement "HOOSIER NAMED TIRE FOR NATIONAL SPEC MIATA COMPETITION BEGINNING IN 2012"

http://www.hoosiertire.com/SM2012.htm

Which at first I took to mean that I could consider Hoosiers, but there seems there could be lag between ICSCC rules based on (Oregon Region SCCA).  Per this discussion on the icscc forum:

http://www.icscc.com/forums/showthread.php?1874-SCCA-announces-2012-spec-miata-national-tire-is-Hoosier&s=5d707879c33d1dda4ce1f1df0fc9c86c

So my question is should I buy Hoosiers for a Spec Miata that will likely do most of its driving at Mission this year?

Rod.

There are only 3 Icscc races at Mission on two weekends. The balance of the events are Cacc . Cacc SM rules require that the cars comply with the current Scca GCR. I would buy the Scca required tires.