Here is the scoop; for the class I'm currently running I'm allowed up to 2.0 liters. The only hitch is the motor had to be legal in a sanctioned series pre 2000.
So I can show L series having been run in Japan.
Improved Production allows A12 turbo (That's what Simon runs correct?)
Here in the USA SCCA allowed A15, which is what I run.
This all stems from my wife's. "Can't you just put a bigger motor in it" comment. I do love the A-series motor and a L-series is a pretty easy swap but I'd like to see if there are other options.