Technical 1954 Mercury Monterey Brake Pedal Assembly

I have a power brake 54 Mercury Monterey which is the Bendix Treadle Vac set up . The booster was toast so I have tried to replace it with an autocity glass brake booster set up that is suppose to be for this car. Problem is the pedal assembly makes for a short pedal that is hard to push. I have plenty of vacuum and everything seems to be lined up correctly but I still coast to a stop. Oh it has drum brakes and everything is new. Thanks

 

What did Autocity say about it?

 

They didn't have any idea of what to do except to maybe modifying parts to fit.