HRCR - OK to "create" a particualr model?

[Duke Caboom]

Anyone know if HRCR register allow the "creation" of particualr models. Could you get a standard Cortina and convert to Lotus spec, for example, or a Mini 850 to a Cooper? I know this has been normal practice in rallying since time began but I once equired about it in a race championship and it very much wasn't allowed.

Obvioulsy would stick to the correct age catagory.