Brake Servo Units

["Mike Burd" <mikeburd@email.msn.com>]

I need some information if anyone could help.

My car has a Girling MK2A brake booster 5".

Why does the later Tigers have the bigger 7"booster? All the brake
components seem to be the same on all Tigers.

My booster is cracked and needs replacing.

I have located a 7" Lockheed booster. Would it be better to upgrade it to
the 7" anyway?

Would I be better to stick with the original size, 5" but a Lockheed?(I
can't seem to locate a new Girling one.(no surprise)
Thanks for your help  Mike