I see.... that stuff is all greek to me!
The total timing on a Mopar is deemed to provide the best performance at 36 degrees total advance. If the motor pings at that 36 degrees of total advance, you either add higher octane fuel, or you reduce the total timing until the pinging quits. Reducing the timing generally reduces the maximum performance.
To get those total ignition timing degrees of advance, you start with the degrees of advance the distributor is set at, then add the number of degrees the distributor mechanical advance adds (which is determined by the weights in the distributor), and then add any advance and vacuum advance might add (by pulling the plate inside of the distributor). Generally, the number of degrees of mechanical advance, and the number of degrees of vacuum advance are not adjustable, but they may be delayed or the vacuum can be eliminated (a completely different story). That means the difference in the total timing is usually set by the degrees of the distributor rotation in the block.
His 392 Hemi has 10 to 1 compression and the motor has iron heads. Generally, aluminum heads run cooler in the combustion chamber, so you can get away with more total timing on lower octane fuel.
87 Octane is the level of the cheapest pump gas and his motor does not ping on the 87 octane if the total timing is set at 30 degrees instead of at 36 degrees. He is giving up a bit of top performance, but can buy his gas at any gas station across the country.
91 Octane is the rating of most premium gas available at most gas stations. Some gas stations do not carry 91 octane gas, if they do, its generally 30 to 50 cents per gallon higher priced. His motor does not ping on 91 Octane gas with the total timing set at 36 degrees advanced. He is not giving up any power at that level.
If the "pump gas" the motor builder says the motor will run on is 93 octane, that means the motor will run without pinging on that 93 Octane at 36 degrees total advance. Generally 93 Octane is not available at most gas stations, it is often labeled as racing fuel and carries a much higher cost per gallon, when you do find it. You may be able to reduce the timing enough to get rid of the pinging if you run 91 octane gas, but at how much power reduction? There will probably not be any way you could run the 87 octane gas without some pinging going on, but every motor is different.