Maybe this helps...
You cannot get 'ping' by just revving while parked and not in gear.
You are probably hearing something else and should advance the distributor back to where it was, if you can.
This will cure your 'backfire' you just created by retarding too much.
Maybe what you think of 'ping' is just an old fan belt that needs some silicone spray or Armorall or simply needs replacing with a new one, if the old one is dried up and cracked.
Maybe the generator needs new bushings or rebuilding or replacing if it hasn't been lubed for a long time.
About the gas - you got it the other way around.
Modern gas is not better, but has more octane, which means you should ADVANCE the timing a few degrees to compensate.
But don't worry about your timing until you get your truck to drive on the open road and more regularly, when fuel economy and preserving the engine condition becomes more important.
If you are just wheeling around the yard, you will be fine with timing that is close but doesn't have to be ideal.
The brakes and steering would be more important to get right at this stage.
Another thing, if you haven't done this yet is to clean and rebuild the carburetor with a repair kit from your local parts store, or just buy one online.
Eventually you will also need a good rebuilt or new distributor.
Old and worn ones can give you lots of troubles, giving all kinds of false alarms.
Same with spark plugs and wires - Get a new set and properly gapped.
Get your basic cheap tools ... like a timing light, rpm gauge, vacuum gauge, spark plug gap gauge, feeler gauge and more than anything: a Shop Manual.
You will learn so much in a short time, if you follow the 'engine tune up' section of your manual, using these basic tools.
