Doesn't make sense to get one without a drum brake. I switched to a SA X-RD3 on my 1973 CCM.
I haven't really compared it to my XL drums that are as good as a disc brake. But the 70 mm is weaker, but better than most calipers for sure.
Anyway, I can do a 100 miles anytime I want with the 3 speed, that is 50 lbs with a usual load. 584 x 38 mm SMP tires.