I thought the intent in Classic was to not allow non-OEM EFI as well as computerized engine management or closed loop feedback to the ECU. But stock OEM stuff is ok. So back in 81 if coil-on-plug and closed loop ECU were stock, ok. But what car had all that stock in 81? And more importantly, would it be sophisticated enough to run it 33 years later without some (not allowed) modifications? It’s probably safe to say this part of the rule is intact and fairly well understood for production class. But Classic allows engine swaps in gas class. That kind of muddies the waters.
Page 70 is very clear that sensor controlled ignitions
“are allowed but must be stock and unmodified in any way for the year and model of the vehicle entered.” Here are pics of one of my most respected Classic cars. Pictures are from records set in 2010. Everybody runs a crank trigger ignition in Classic. (Even with carburetors). However, crank triggers are Hall Effect
sensor triggered. So non-stock, modified, sensor controlled ignition are being used in all classic classes.
I think the intent was to not allow,
distributorless, COP, computer controlled ignition, regardless of engine swap. That is quite a bit different from an MSD trigger wheel firing a distributor. But I don't know now.