Hi, Good luck with that. I have a 4 bolt master cylinder that was new in May and then the servo packed up. I then bought a complete servo and master cylinder had it fitted only to find that after 1990 they changed the servo. That meant the brake pedal is physically lower than I would like. I would suggest you check the Peter Russet book to make sure you are getting the right one.
I may be able to sell the master cylinder if you are interested.