There is a lot of history in Charlie Yapp's Secrets of Speed magazines.
https://www.secretsofspeed.com/secrets-of-speed-society
I don't think there is any difference between the terms "power adder" and "speed equipment" - they both relate to increasing performance.
Four Ever Four is a MAFCA chapter dedicated to the preservation, celebration and promotion of early Ford four-cylinder vehicles. As a club it's 5 years older than MAFCA.
https://www.foureverfour.com/history/ You'd be amazed at what these guys are still doing modifying combustion chamber design, cam profiles, etc. SCTA has classes that specifically require vintage blocks - no Burtz or Donovans.
Here is the new V4 record setter at 174.6 set 4 days ago. V4 has OHV V4F is the flathead 4cyl. That record is 115 set in 2020. The lakesters with these engines run about 20-30 mph faster (140 on El Mirage).
https://www.youtube.com/watch?v=fn9yB8VmMnM Here is a 2013 video of a flathead 4 Streamliner setting the record at 133
https://www.youtube.com/watch?v=d8NnnpT1KQU
There was also the Russetta Timing Assn. It was started because SCTA did not allow closed cars to race. It lasted until the early 1960s.
MAFCA Modified judging class:
5 Carburetor (up draft or down draft/single or dual era).
6 Intake manifold (up draft or down draft/single or dual era).
10 Exhaust manifold headers.
15 Any non-stock era head, originally designed for an A, B, or C block (finned, aluminum, overhead, or any pre-war head of a non-Ford manufacturer, such as Cyclone, Chevrolet, Miller, etc.).