K10 disc brakes on my 65 swb K10

[K10-BB*65]

Trying to get some information. I converted to disc brakes and larger rear drums using the front and rears from a 76 K10 along with the master cylinder, and proportion valve. I used a smaller booster from a sixties impala since I didn't like the big truck one and the big bracket that makes it stick out from the firewall. Problem is the brakes take a lot of pedal pressure to stop. It doesn't seem any better than the stock 4 wheel drums. Any ideas? Maybe need a different booster? The discs and calipers are new as well as the master and wheel cylinders.
Thanks