Set "total" timing on a stock 318 two-barrel where?

All I can say is regarding ideal timing as recommended here, been messing with a 78 Magnum my son recently picked up with a 360, unknown lumpy Erson cam, Demon Street Demon 625, duals and unknown compression or supposed aftermarket pistons (likely below 9:1) the initial timing WAS at 10°, the idle speed was cranked up excessively and vacuum gauge at idle was barely @10. After yanking the points! distributor apart we discovered stock springs, a 19°(38°} cam/plate! So it was at 10° initial, the plate added theoretically 38° at when? and then the vacuum added unknown advance. All over and just shitty. So I welded the plate to yield 9°(18°) yanked the heavy spring and added a Mr Gasket 925b, marked the balancer, and set the initial at 16° and adjusted the vacuum to add about 10° all as a baseline based on reading elsewhere and here. 16° initial, 34° total and with 10° vac advance for part throttle. What an improvement, backed the idle down, tweaked the idle screws, got 13 inches, thing cranks instantly, even when hot and recranking after some heat-soak, idle is strong, in park and in drive, sharp throttle response, and a few runs up and down the road revealed no pinging anywhere, so much better and now ready to really dial it in. Read up and apply the knowledge from here and elsewhere. It works.