I have a 54 Ford that I converted to manual disc brakes in the front. At the same time I changed the rear brakes to a wider shoe/drum. This is a very heavy car, much more weight than yours. I used a non-power disc brake master cylinder (two bowl).

I am very happy with this setup. Yes, the pressure required is more than with a power brake setup, but less than the old drum brakes on all four wheels. I had a major emergency requiring to me slam on the brakes doing 65 mph on an interstate and the brakes came through with flying colors (it stopped the car quickly and without hitting anything.)