This is a better shot of P1076.
The two "odd" Rover striker parts shown above are evidently not present. I say odd because they are not the usual standard ones on most original GT40s anyhow.
The photo below shows clearly enough that JWA had dispensed with the Rover claw latch, presumably to solve the historic problem with the doors opening or lifting at speed.
The "Silent Travel" latch mechanism has a spring loaded bolt which enters the hole in the tapered striker providing a more secure lock. The loop ended lanyard tied to the roll bar is also placed over the top lever in the window frame as a keeper to prevent to bolt reversing.
The fixing bracket is joggled to fit the inner profile of the striker.
I would assume that P1075 was furnished using the same fittings by JWA.
You can also see the Silent Travel / MG latch fitted on the inside of the door skin in the top left of this photo.
I might add this refinement to my own car however I would make the striker in steel as the OEM part appears to be cast.