I’d be surprised if it was a 2.8 in California. It looks like originally imported into the US and to my knowing the anaemic 2.8 litre scrooge version was not even available for the US market. Tach and engine are 4.2 litre as well.
The stickshift box transforms the car a lot. Obviously someone was after that in the past, as the triple SU setup is not easy. In general, manual gearboxes are sought for, but the original boxes were mostly overdrive boxes. It looks as if your car has been treated to some throw-in solution, however. The non-original pedal box is one give-away.
The California climate has left the original and valuable interior to be rescued it seems and the body looks very good except for the rubber strips over the doors - are they just glued or screwed on? Usually, there’s rust around the eyebrows, along the window edges, lower edges of the hood behind the wheels, inner and outer sills. The bit of surface rust along the rear quarter panels and the rear valance is easy to fix.
Would make a very interesting project for restoration to original outer appearance.
75 XJ6L 4.2 auto (UK spec)