It's a 9000 series Pantera, very possibly a factory GT5, but obviously very modified. I say if you like the car and have an acceptable price to buyer and seller, purchase it drive the hell out of it and enjoy it! As for originality and investment grade, I think the mods take it outside that now, but then again a RHD Pantera is a rarity in it's own right.
I must admit I hadn't picked up on the Chevy power, that would be a deal killer for me, but there are a few diehards who have made the swap.
The shroud for the fans is over rated IMO, they actually restrict airflow over 150mph, especially with a single fan and a shroud blocking so much of the radiator surface area, what I would do is fabricate a proper mount as the through the core ties will eventually destroy the radiator.