No new classes for touring, cabriolets, etc.
A roadster is as Tom found in the dictionary. Single seat and all that stuff. A roadster pickup is allowed because the cab will accept either a roadster body or pick up box. A '27 cowl with a '26 body would not be either a '26 or a '27 would it.
If you need a roadster definition in the rulebook it will not change anything, same rules and more words. This is not that difficult.
DW