Brake Booster hard pedal

[ipoppa33]

Hello been lurking and reading posts since I bought my 70 swb in Jan
already done a few things (hood spring).


Been trying to get a handle on what the previous owner did and didn't do... oh boy.
Not sure what the truck came with stock but it has discs in front and drums in the rear. Anyways we finally got part of the brake problem figured out- the rear cylinders were shot. Got new ones and re-bleed the lines and the truck will stop but doesn't feel like the power brakes. The booster is small, it holds vaccum. Have adjusted the rears and checked the fronts and everything seems fine, just doesn't stop great (can't lock them up and the front end doesn't nose dive like I think it should with discs).
Is this brake booster the correct one or should I get a larger one? Or is it something else?
I appreciate the help, thanks.