Did this to my 69E. 964 Brakes. But I had 3.5" brake mounting from my Al calipers. If you have the 3" mounting for a stock T strut the you will need to buy struts with the 3.5" spacing. You will have to get a 964 rotor(24mm thick instead of 22mm) Also the mounting holes on the 964 brakes are 1/8" wider than even the 3.5" struts. So some adaptation is necessary.
Do not change the Master cylinder. It will work fine. A pic.