Is there a series for GpA / Pre '87 saloons?

[RacerRich]

or more precisely, it's a difficult area.

Around 83-87,there were some great cars racing, but although in the British Forests, a Group A machine was pretty much a road car, heavily modified by the chassis builder, and adorned wtih HOMOLOGATED Gp A bits and bobs, it seems the series for Group A race crs was completely different.
They were still built to Group A, but errrrr, that's where the similarity with a Road car, Group N, A or anything else ended.
Huge wheels/tyres,/brakes/allow hubs/with single fixing nuts, chassis set ups from the land of make believe, and so on.

So could someone please enlighten me of the rubicon between Group A (as a formula and homologation) and a series like the old RAC BTCC.

Thanks