There are two ways to remove your drum, with or without the hub. You didn't mention what you had done there.
Without the hub: There are two slot screws through the drum into the hub. Usually thouroughly rusted and require one of the hammer type impact tools to remove. This should free the drum from the hub and allow you to tackle the brakes.
With the hub: Remove the 8 bolts holding the axle, then pull the axle out. Inside there are some large nuts with keepers that tighten the bearings. Remove these and the hub/drum pulls straight off. It's heavy, so be careful it doesn't land on your foot.
As for disc brakes, there are no kits. We had someone post a website where someone was making his own, but his setup was unsafe. I tried e-mailing him, got no response. Too bad these old trucks are so narrow, I would love to put a late model front and rear under my 52.
