Power Brake Conversion Question

I had bought a kit about 10 years ago, to change the manual master cylinder to power/dual master cylinder for my '61 Impala. I had put the '61 on back burner and have been working on updating my 1948 Chevy Conv. It had disc brakes, but manual dual master cylinder. The car was hard to stop, so I decided to use the '61 master cylinder and power booster from the kit on the '48. The '48 stops great, but there is very little brake pedal feel. Could this be the aftermarket pedal that was used, or is there something with the power booster. Boths car weigh about the same. Any comment would be helpful.

This most likely is a pedal ratio difference betwwen your aftermaket pedal and what the impala booster uses.