lurcher

Hi i'm new to this and not long brought my first landy, a series 3, its had a few modifications by its previous owner, a 200tdi engine and LT77 gear box. there lye's my problem, my speedo does not work, my landy still has series 3 clock, can i just go out and buy a cable that will fit the gear box and clock. any help is much appreciated. thank you. Mark.