Less than a year for the GT/J "B2" then. This one and mine were A-reg, so must have been registered right at the end of the changeover (that's what made me think they were run for a little longer). Almost all registered would be Y-plate in that case.
It was more dark grey, but it was a different material altogether than all the other trims. Looked like the duffle coats we wore in the late 70s early 80s. If anyone has the red Manta brochure from 1982 you can see the seats of the GT/J in all their basic glory--as well as how each model was specced.
Hey, check out the side door decals they had. The reproductions were even discontinued when I was trying to do mine in around 2008-9 so I was busy making up templates, not realising you can easily make the J from the G on any manta decal. I later got a tattoo of my daughter's name, Millicent, all in the Manta font by simply using the sections of GTE decals.
Supplying 3 is technically wrong as has been said, the "Manta GT/J" or "Berlinetta" appears only on the side, and "Manta 1.8S" on the rear; not to be confused when we're saying 1.8s to describe 1800s.