No.62 heads have 72-75cc combustion chambers, which will yield 9.8-10:1 compression on a 400- too high for 91 octane (hence the pinging). A few cams that will help lower your dynamic compression are the Summit 2802 and Crane 283952- both have a 114 degree LSA (lobe separation angle) and 224/234 duration @.050, which will limit excessive compression and help somewhat with the detonation.
Thicker head gaskets won't help your detonation issues, since you're well over the 9.5:1 limit for 91 octane. This limit for iron heads assumes you're tuned correctly, but if you have sharp edges in the combustion chamber that cause pre-ignition, excessive timing, or even stale gas you'll still get pinging. I've noticed even 9.2-9.5:1 engines running on 91 will still ping a little on hot days (I live in SoCal where summertime temps range from 95-105F), so I try to limit the SCR on most of my builds to 9:1.
Geno
