What brake pads to use for Kelsey-Hayes setup?

Problem being its fifty year old technology will never stop like your Toyota. Without tons of money and modifications.
Has brake technology changed that much since 1950's? Fastest you can stop is to brake just before the tires skid. Even 9" drum brakes can skid the tires. Next importance is if braking is balanced left to right and the rears are proportioned correctly to skid just after the fronts. Anti-lock braking is the major newer technology (~25 yrs old) that our cars don't have. It compensates for unskilled drivers who would skid when they should pump the brakes to avoid skidding. Studies show it doesn't work well in practice since many drivers are scared by the strange feel (like something is broken) and let up on the braking.

A bigger technology difference is tires. I read a recent article where special snow tires were tested against All-Season tires. The snow tires reduced stopping distance by half, which is tremendous. So if you really care, study your tires. Obviously, you can't compare old braking data on our cars measured with skinny bias-ply tires. I am sure they stop faster with modern radial tires.