Which power brake booster

Would like to add power brakes to my recently purchased '51 Mercury and I don't think it should entail spending $500 or installing a new front end under the car. Subscribing to the KISS philosopy I'm thinking that installing a power booster and petal assembly out of a Ford truck and running new lines should do it. I would appreciate any feedback before I start this, expically suggestions in the area of which booster/petal asssembly might work best.
I've looked at the MPBrakes website and they offer an under-the-floor power brake unit with 7 inch dual boosters but I get the feeling that that unit would not be sufficent if I wanted to install disk brakes later on.
Any thoughts/suggestions woul be appreciated.
Charlie Smith