Really had nothing to do with gas in the day, versus now. Though it is different. That was CAP, Clean Air emission standard. Chrysler's method for improving idle emissions. Leaned out idle and low speed carb jetting, and less initial timing to burn product in a hotter exhaust; and sometimes higher idle, hence a solenoid on some models.

So for a complete answer is this the original distributor? If so the mechanical advance is much more then the earlier cars. 30deg total for manual according to the spec. You can certainly add more initial and still keep total in the 34-36 range depending on how your motor likes it. But make sure you know how your carb was set up too.

If you want to go performance oriented, then your going to need more initial, but your recurve really means a new cam stop with less mechanical advance... or welding up the slot on the current one if original. If you don't and lets say you go to 12 or so. You will be advancing way too much and wind up with 42 total at minimum and that is with no vacuum advance. Pushing you into detonation range.