I think it's genuine, but a couple of comments. Looks like a partwork model, with a works 205 T16 rear bodyshell on the roof, which was later than 81 - 1984-86 seasons with various liveries. Most of these partworks come from the IXO collection of brands (eg Altaya is common) and IXO have just announced a revival of their works Talbot Sunbeams from the 1981 season, including an associated Talbot team van (IXO Citroen C35 - 1981 Talbot Sport Rally Assistance 1:43, product code RAC369) - it's not out yet, but pre-release pic of real thing with a glimpse of a Sunbeam here. IXO often try to spin multiple versions from one base casting, particularly if there's a partworks commission kicking it all off, so there could even be further versions in the future.

Talking of partworks, I've just seen advance announcement for what I think is the first ever model in 1:43 (or any other scale??) of an Austin Montego - looks like an Italian partwork with LHD and a dull green. But if it's another from one of the IXO brands, there may be a proper release later with upgraded detail/livery.