IF that is the original distributor from '73 then there should be a tag on it. which I did not see in your photos but from the angles thats not surprising. https://www.forabodiesonly.com/mopa...s-rotor-turn-in-the-distributor.514677/page-2
For an automatic it was p/n 3755042 it was TDC @ 750 rpm plus minus 2.5 degrees depending on conditions.
It probably had EGR. If you're not using the EGR valve then depending on the system the EGR may need to be blocked.
Whether this has bearing to the pinging depends on the circumstances pinging or gurgling is heard.
Most EGR systems worked only when the engine was warmed up, and warm or cold there was no EGR at idle and full throttle.
There is information in the Master Tech Series as well as the '73 Chassis Manual which should help figure out what is need to block off the EGR (based on what I see you don't want to make use of it for your car). Maybe its as simple as leaving an old EGR valve on the engine because its normally shut.