help hard break pedal weak breaks after swap

I went through this. I have 74 disks on the front of my 67 Barracuda and 74 11X2 1/2 drums on the rear.I orginally had a 1 1/8th bore master cyl and very hard brakes. I dropped down to an smaller bore master cyl. I found a 7/8" at Carlisle and swapped it out. After a lot of bleeding (you'll have more pedal travel) I finally got it right. Mine are manual brakes and do stop well, but it does take more pressure then your power brakes. This year I want to play with a adjustable proportional valve to the rear drums.