A similar problem to mine with my Works Rover. The BSCC regs were based on the homologation papers plus any homologated mods. Ford f'rinstance homologated the IDA as an "export" option. They also inserted 7" rims.
Rover OTOH came along in 1980 and homologated very little. They relied on the Blue Book and App J. Now the MSA is effectively denying all knowledge of the class. Only Goodwood and MRL currently recognise its existence.
I do know that the FIA is trying to sort something out but with all due credit to them, they are also struggling to resolve it.
Good luck with your quest. As for me
Edit. Welcome to the forum.