28* initial timing for a 318? How can that be?

Mattax said
If the distributor was setup for the cleaner air package (CAP) then it was meant to be used with a retarded initial timing.1 In those situations, sometimes a manifold source is a quick and easy way to get initial back up where it would have been pre-emissions controls. I've posted graphs showing that - you've probably seen them.2

FBO kit: Although he has changed his kit and recommendations over time, he's still only partially correct. It's impossible to have a discussion with him. He's come on here several times with his diatribe and then disappears when a real discussion starts. His plate design is the reason a factory ECU seems to retard. Its also the reason for many years he said it couldn't be used with vacuum advance.3

1. See the Master Technicians Service Conference. Hard to beat the factory info when looking for good information. If you can recall pre-internet how difficult it was to find technical service bulletins and factory tech info, its easy to understand why a lot of speculation and assumptions were made by hobbyists. See for example 1967 Combustion in Today's Engines and Introduction to the CAP Story. Timing is also discussed in 1959 Introduction to the new distributor, and 1970 Lets Keep it Clean.
Available at the Online Imperial Club linked above, and mymopar.com
2. 1967 Service Manuals have timing specs for both CAP and non CAP versions of most engines offered that year. Graphs comparing the 440 Hi-Po timing
3. Videos showing what happens to timing with an electronic box when the distributor's advance is stopped early Lets Revisit Timing

Thats it, i feel the curve in my car is too quick, the reason i had to knock it down from 34 to 32 all in. That mechanical curve is why i am afraid of the vacuum can being attached, it came unhooked, i believe the previous dist tuning was for lighter springs and "all in by" a lower rpm than what actual maximum power could be. I would like to try a more graduated curve and all in by 3500-5k where its making max hp, leaving a lower advance # as it passes max torque. The part that confuses me is when Vac advance is added it should make up for the higher initial just off of idle, so my thought is a lessor initial shouldnt matter if using vacuum advance except for a good smooth idle as even on ported vacuum the advance will jump up as soon as rpm is raised past 1000 rpm or so. so a heavier spring set may actually help power over a longer curve when using vacuum advance. But everyone suggests a higher initial, do they use heavy springs? or just leave power on the table? with total timing max before hp/rpm? Max torque on a 340 would likely be around 3000 and max hp would be around 5000, I would guess somewhere around 28-30 degrees at 3k and 34-36 degrees at 5k. Why does everyone suggest "all in by 2500" ? especially if running vacuum advance and "easing into" full throttle to maintain traction.