9.5 comp with alum heads. That's low so you can run low grade pretty easy. The performance will suffer though. HEMIs are different than wedges, you can run 10.5 comp easy with 92 or 93 octane with those heads, and with full advance on timing. But then again I don not know about your octane ratings. Don't bother with a big cam with that compression (9.5), your wasting your time and fuel.