Many if not all already know this, but the Triumph TR3 (late) master cylinder fits my Grantura MKIIA and likely most if not all the other early models. The master cylinder is Moss Motors part #581-010 and fits either the brake or the clutch side. The reservoir part number is #582-980. When the master cylinder is fitted, the old push rod is retained since the new push rod is about twice as long. I changed over my failure-prone brake mater cylinder in about an hour.
Tip: prefill the m-cyl with brake fluid before installing it, then jack up the front of the car for 12-24 hours then the back for 12-24 hours and the system will actually self bleed! (I didn't believe it myself till I tried it. Even if you still need to bleed to get the last air bubbles out of the slaves, the job is quicker and easier.)
Bud Michael
bud@vnet.net