440 detonation issue

well im now the new owner of a 72 d100 se .it original 400 has been swapped to a 440 which wears hi-po ex manifolds,and judging by the balancer has a forged crank.other than this the engine is an unknown ,the builder is 6 feet under.the problem im having is it pings under full throttle no matter what i do unless i limit total timing to about 22*.this puts initial at 2*atdc.i randomly pulled 2 plugs at it cranks at 170+ psi.i think the problem may be a high compression ratio and a short duration cam.i tried fattening the mixture to no avail,checked plugs for the correct range,ran with the vac advance disconnected,etc.im out of ideas........