This topic is also on the Stock group. Here is my response to that one:
I wrote Girling/Lockheed years ago. At the time, there were a number of servos on the market. If I recall, there was a 1.9:1 ratio, a 2.3:1 ratio and a 3.0:1 ratio. Victoria British sold the 1.9 one, Sunbeam Specialities sold the 2.3 one, and you'd have to go to a Jaguar place to get the 3.0 one. Girling/Lockheed wrote back and said the 3.0 one was the correct one for our cars. I also had other papers at the time that I'm pretty sure supported the Girling letter.
I had already purchased the 1.9 one. So I tried it. I didn't like it. I took it out and put in a smaller ID master cylinder and have been happy with that ever since. But my Tiger does have a servo that works nicely, and I must admit I like it perhaps just a tad better than the Alpine without a servo.
Separately, I do have Dan's rear disc conversion. But I simply haven't been able to get to work on the Alpine (and need to call Dan about one of the parts). On the plus side, I've continued to enjoy the Tiger in the meantime.