I'm working this out myself just now...
I'm waiting on a GM tech to give me the specs of the C6-Z's master for comparison to what the market is offering. I Love the new Wilwood tandem but they offer 7/8" 1" and 1.125" and i cant make up my mind!
If i was to run the stock style set up (7-8-9" booster and mc) i probably could use a 7/8 but with HB i've bee told 1.125"
I just don't know and don't want to do this twice. I found a nice site that takes you theu the procedure to find the right size MC but its a hard and long list of calculations in and out of the car...
...'Guess i should stop typing and get in there...

Lead.
Hey, correct me if i'm wrong here but, if you get a HB unit it doesn't matter the size of the cam, as its running off the power steering pump system. Thats what makes HB interesting, no? (Paul, Hydratech?)
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LEADFOOT1
New for summer '13. My latest find!!
48k miles, 100% original, 1969 Camaro coupe. Untouched, never apart and squeaky clean!!! 327/th350, A/C car. Gold on black w/vinyl top. Only add ons; Fast ratio box and SS396 wheels.
FINALLY!!! A car without rust repairs ever!!! None before, none coming!!! Cant come to modifying it tough....
...So, '67 Camaro project with my laying around stuff out of my black 'vert. 468 BB and YSI blower, braked th400, 12 bolt/spool, 35 splines etc. Complete Calvert suspension front and rear. 30x13.5 ET Streets, caged, lightened, slammed and running low 9's "Street car"