Front brake pulsation - steel vs cast (??)

[1953M100]

Bought my 1st Model A couple weeks ago. Previous owner replaced the drums with new cast iron about 400 miles ago. I have put about about 20 miles on the car, began to notice a pulsating brake pedal and significant "surging" when coming to a gradual stop. Raised the front axle, and I can definitely feel an obvious oscillating "free-drag-free-drag..." rotational difference when I spin the front wheels. Took the drums to O'reilly's for re-machining. The guys there are saying they are steel drums. Based on photos and searching here on the forum, to me the look like cast... (??)