Most alternators have two threaded connections on the rear next to the main wiring connection, which allow you to connect up a rev counter etc. I know my 2.5TD 90 has!

I bought a landy over two years ago a G reg 90 2.5td with 138000 miles on clock, it is the coolest vehicle i have ever owned, to be honest i DIDNT need one and was very hesitent about buying it, i should not have been. I used it every day for over a year to get myself to work 50 mile round trip...