Yeah. I paid $100 for a bracket kit and then spent at least $400 more on new parts to feel good about my brakes. It was long enough ago I no longer remember what I spent total. You really need to convert to a dual master at the same time, which means you'll be re-plumbing at least part of your brake system.
I have a dual power setup in there now, but its drums, and I'm not liking power with manual adjusting brakes. I can get parts cheap so I just need to know what parts from what car/truck I need to look for.
I used '73 Chevelle rotor and caliper and outer bearing on mine. The inner bearing with seal and a sleeve that went on the spindle, along with the caliper bracket all came in the $100 kit. The kit said mid-70's mid-size GM, I chose '73 Chevelle because I was already using a '73 Chevelle rear. Master is the same car too. All the brakes parts were new when I put it together. Brakes are too important to cheap out on used parts. And they don't cost that much anyway.
I found a kit on ebay that is about $280 + $70 shipping. Probably can't do it for much cheaper, but if I know what parts these are I can spend the money over some time. I get a pretty good discount from my parts people.
The dreaded Speedway motors sells a nice kit that I installed on a customers 50. It bolts up well but does require you to run 15in rims that are for disk breaks.I also converted to a duel reservoir master at the same time.