Will, If its an ITA Civic. Why not race it as an ITA?
As far as Lemons/Chump cars go the GCR has rules, even for region specific classes, and if these cars are not rules compliant I will have no problem writing a stack of protest. The supplemental regulations can only compliment the GCR, not contradict it so the region/race cannot make non-compliant cars compliant.
I am certain some Lemons/Chump cars will be compliant, some not......