Advance the timing before TDC. Why?

With it cammed up even 9BTC is likely not enough for "best."

TDC is a smog setting. If you go download a few service manuals from MyMopar, and get back into the electrical section "specs" You'll find that this zero crap came about sometime around after '70...when engine emission controls came about in '68 and got tighter year by year

Some smog stickers called for timing to be AFTER TDC

Retarded ignition specs are about SMOG CONTROL and not mileage or performance.

There is a "famous" thread on here about timing you should read. See if someone can find it............see post no4

Ignition timing chart