I'd like to see what
@itey says about your timing curve.
IIRC he has a lot of experience with the SBF and
I believe he says timing shouldn't be all in until high RPM on those motors.
I hope he chimes in, it's something I just thought was interesting at the times.
In bracket racing none of this matters because all you want is the car to repeat the number, but if you are racing in a rules limited class where everybody is using the same small carburetor it is a significant advantage, but beware of triggering the tech inspector who will go crazy trying to find where you are cheating air into the engine. This can actually be humorous.
Every engine is different and has its own appetite for spark timing, but nearly every NA engine needs less advance at peak torque than at peak HP, so runs best with an advance curve adding timing through the power band RPM range.
Several times I have quoted the Ford "Muscle Parts" advice for the Boss 302 as an example of an advance curve which has a very profound effect in eliminating the myth "ports are too big to make good low end torque" which is the result of when an "all in @ 2500" curve is set for best power at 7000 RPM it is about 7 degrees too much advance for best power at 3000, and this is so even if the fuel is high enough octane it doesn't knock with too much advance for best torque output.
I have experienced newer cylinder heads, stuff designed (and zhyneze copied) in the last 10 years or so, with "fast burn" chambers that show a distinct need for a curve that adds timing after the torque peak. This has been the case on both engine and chassis dyno and the butt dyno. (smart phone accelerometer, get the app to measure HP with your phone)
With points, locked or "all in early", holds the same timing as RPM climbs, but ironically, an analog electronic ignition, induction or CD, retards as RPM climbs, usually about one degree per 1000 RPM.
The retard is because of the slew rate of multiple electrical components and transistor switching delay, which causes the timing to retard as RPM climbs. The advance mechanism can be arranged to compensate for the slew rate.
Ford advice for the Boss 302 is 30 deg at 2000 with a straight slope to 40 deg at 8000, so that is 1.66 deg per 1000 RPM. Coincidentally, Bill Jenkins (what would he know? and the Ford engineers are nuts too?) advised 1.5 deg per 1000 for the SBC, like the engines he built for drag racing and circle track.
I have been doing curves like this for nearly all engines for over 50 years and a guranfawkingteee it is worth the time if you can use a distributor machine, particularly if the engine is a little or a lot restricted in the carburetor or intake system so it has rising intake vacuum with RPM increase.
Unfortunately, this is not easy to do with a MSD distributor. The GM HEI and Ford Motorcraft distributors are the easiest, the Ford back in the '70s when the springs were available from Ford and the part numbers were the same as used in '65-'66 Galaxie 390 300 HP engines, so they were usually in the bone pile. Nowadays I get springs from the hardware store and cut them to the number of coils required for the necessary spring rate.
