I picked up a couple of XJ6 electronic tachometer from a scrap yard for £30. My initial thought was to fit the innards into my originally tachometer, but that will not work as the electrical bits are to big. The main differences are the oil and ignition light positions are missing from the Jag instrument, and the needle is a different style.
My car is my daily car and far from concours so I am using one of the Jag rev counters as is with the lights on a separate panel, and then plan to swap out the face and needle on the second one at some point for future fitment.
George