Ok, it all makes sense now.
Vintage engine in A vintage body class requires no turbos, no engine management, etc.
A vintage engine in a vintage body in a modified class, IE Altered, Competition Coupe or Gas Coupe with and X or XX engine running EFI, TURBOS, etc, is allowed.
Am I correct?
So If I want to bounce between Competition Coupe XX or Vintage Gas Competition coupe switching between carbed or EFI will do this class change correct?