I had the same detonation problems with my 70 Bonneville. 1970 weas the only year of the high compression 455, and it did not like 93 octane fuel. I monkeyed around with octane boosters and timing for a couple years. Then I got a 6X heads with large exhaust valves, street ported and enlarged bowls to lower compression my Jim Butler. That corrected the pinging.
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