On my 420B, the brakes had been cannibalized off of it by the time I bought it. I bought band type brakes off of a 530 thinking they were a direct fit. I had to take the covers and modify them on my Bridgeport mill to make them fit and to rearrange some tapped holes.
It was worth it, however. I could make the brakes scoot when applied if I could keep them dry from the leaky seals.