I want to second your comment about using a series II master cylinder. ( I think it can be a series I cylinder too.)
If I recall it has a bore diameter of 5/8" (.625") which is smaller than the later cylinder used with the booster. The smaller bore gives you higher line pressure than the bigger cylinder , with the trade off being slightly longer travel. I have driven my 66 Alpine like this for many thousands of miles and quite like the brakes.
If I recall when I bought the new earlier cylinder back in the days from Doug Jennings it came with a different pushrod. I think it is necessary to use the original pushrod but you will find that the heavy washer which goes under the circlip at the back of the master cylinder is of course slightly larger than will fit on the new cylinder and the washer is trapped onto the shaft of the original pushrod. I remember reducing the diameter of the washer by holding its edge against an electric grinding wheel and letting it rotate against the wheel. If you hold the pushrod steady you can take off a controlled amount of metal from the circumference of the washer until it is a comfortable fit into the new cylinder. This sounds a little funny to do but worked fine.
And hey, if you are not shooting for concours leave off the bad booster and have a little more room under the hood.