Not the only Plus 4, T16 in North America.
My 1994 purchased new in Virginia and sold my sold May, 2015. It went from Maryland to Illinois.
I just cleared out some paperwork last month including Rover 800 series workshop manual I obtained in the UK.
Believe Rover 800 was front-wheel drive sedan.
I had no luck finding oil filters on this side of the Atlantic but readily available online.