Power Brake Booster won't boost

[Lil Wet Cowboy]

I converted my 1969 351W from two barrell to a quad and just couldn't get it to idle properly. Turns out the power brake booster was leaking so I replaced that huge old Bendix with one of the newer 9" boosters that is supposed to work with all 1967-1970 models. Well, it doesn't. The motor generates 16psi of vacuum at idle but the pedal is hard as a rock. I know things are sorta working because when I start the car with my foot on the pedal it depresses slightly. Will the addition of an electical vacuum pump help?

 

[General karthief]

Sorry, didn't look at this, sometimes I don't get alerts.
I'll move this to the classic forums.