I believe that the factory power booster has additional linkage and a bellcrank of sorts that mounts between the firewall and the booster. From what I remember the booster doesn't bolt directly to the firewall with a rod to the pedal.
I don't think that part comes with a rebuilt booster. You will probably be better off getting an an aftermarket unit unless you can find this additional hardware.
Fred


1956 3100 Pickup/Red/350/3sp OD/PS/Disc Brakes
1957 Bel Air Sport Coupe/Red/355/TH350/PS/Disc Brakes
2017 Silverado LT Single Cab SB/Black/5.3/6 Speed Trans
1947 Willys CJ2A w/F-Head engine