I paid less than $100 for a dual master conversion kit, which included a bracket and linkage.
Since I was converting to disk brakes on the front at the same time, I was able to get an inexpensive rebuilt master that was less than $50, which seemed cheap, but a year later it still works fine.
I bought a 25' roll of tubing when I did mine, and I ended up buying a stick or two separately, but I think it was because I needed fittings I could only find locally that way.
My disks, master cylinder and rear brakes are all '73 Chevelle, so some of the specifics of my install might not apply to anyone elses.
When I converted to disks I discovered the original master had a 10 lb residual valve, and one I applied the brakes the disks would not release until I undid the brake line.... That's why I went dual master.
