I am guessing here but is the servo the master cylinder that supplies the hydrulic(sp) pressure to the wheel cylinders? If that is the case then power boost(vacum or otherwise) makes no difference. What you have to look at is the bore of the master cylinder in ratio to the wheel cylinders. If you are operating drum brakes at all wheels then try for a 1:1 ratio. For disc brake setups try for a 1:2. ie drums 1"bore master 1" wheel cylinders, disc 1" master cylinder to 2" caliper piston. In a disc/drum setup you will need a proportioning(sp) valve that came with a similar wheel cylinder/caliper bore combination. The next ting to consider is the pedal ratio. Try Wilwood brakes' web site for an explainationof that, it isn't hard but it is involved. I am assuming that you want about a 75lbs pedal pressure. Another option would be aftermarket master cylinders. I am running a CNC dual master setup on my 63 Scout and have been very pleased with the results. Happy Hot Rodding.