Torque convertor and detonation

AJ, post #15. No, not race timing. Not at all.

Failing to use Man connected Vac Adv was an engineering error by Mopar. They didn't make many mistakes, but they did with this. GM cars used MVA. That means whatever timing the VA added was added to the initial timing & that was what the engine idled with.
Lower CR, more cam, single plane intake all need more idle timing. My 1966 GTO left the showroom with 26* of idle timing: 6* init + 20* MVA. It had 10.75 CR & a very short duration cam. A 9:1 engine with longer duration cam will need more timing.
The OP has already stated his engine liked more initial timing [ they all do when it is too low to start with ] & that is his engine sending HIM a message...
The LS engine with a modern, compact chamber, 10+ CR, idles @ 22* & only requires about 27* @ WOT.