is 11.2:1 compression too much for 91 Octane

I wouldn't be too worried about 11.2:1 static. I'd be more concerned with what your dynamic CR is. That will tell you more about what fuel you can run than static will. For example, my setup is a stroked SB 11:1 static, iron heads, 91 octane. What makes it work on 91 is the big cam that brings the dynamic down to 8:1, efficient combustion chambers, quench, etc. I don't run it down the track with 91 though. Will always swap in race fuel for that. Although I did open it up and ran it to about 115 mph with 91 octane on a back road and never heard a ping out of it. See if you can find that cam card though. That will help a lot.