Brake Help

I purchased a remanufactured unit from Rock Auto for Power Drum Brakes, and it is the one with the smooth zinc phosphate booster. I checked it with my old brake bracket and the rood is too short and also the backing plate I have is the stlye with the studs in the top. I know there is another style without studs but is there a stock relocation bracket that is installed behind the booster in the engine compartment side. Are there any missing pieces or such that I missed? Any input would be greatly apprieciated

Is this a replacement or are you swapping over to power brakes?

The car's fender tag stated B51 but it had manual brakes when we bought it.

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