As a matter of originality, the original rubber door buffers on MGA had a little curl on the extended front to wrap around the edge of the shutface plate, therefore shielding the interface between the back of the door shell and the shutface plate (as shown in these pictures).

Most of the modern replacement door buffers (at time of this writing in July 2018) do not have the curl or the extended front edge, commonly stopping about even with the front face of the shutface plate. Some of the modern parts are also too thick, preventing the door from closing flush with the rear fender.
With some careful grinding or sanding the rubber can be made thinner, as original.

Correct replacement parts might be available, but so far I don't know where to get them.

Pictures below show original and current replacement buffers together.