At 9.76:1 you will not be running 89 octane in a heavy truck with an 8000 lbs trailer. The thing would run so poorly if it didn't destroy itself. Plan on running the highest pump octane you can get in your area. Cam timing will have a lot to do with how the engine runs, octane requirements, and detonation resistance. What can are you thinking of running?

Also, I would recommend doing a mild exhaust port cleanup on the heads and polishing the chambers will increase detonation resistance.