Drum brakes working at the designed usage, works fine. Even with out power assist. If the peddle ratio is correct. At least 6-1. A lot of times they will stop better than disk. Disks come to there own, after repeated hot use. Parking lot racing, ect.
Some of the so called KIT's have stopped very badly, after install.
Also if you have a lot of cam, you will not have enough vacuum, and the booster will be useless.
This advice comes after 100s of installs. Disk brakes biggest benefits: cool looks, and less fad, after repeated use.
Also less critical adjustment, for pull.
Dave Tallant Hot Rod Shop KC Mo