Scarebird has been making these products for a while now and I've heard decent things about them. It certainly is a better deal than some of the other full blown kits out there.
I wouldn't woory too much about bearing spacers. Use some green loctite and they should work out okay.
You know, the AR Engineering 11.75 Viper kit is designed to use drum spindles. You can get the caliper adapters for around $180. Depending on the source, Viper calipers are around $500 a pair used. Throw in a master cylinder and you've got world class braking for under a grand. Wilwood also makes kits that have bearings specifically designed to fit the small bearing drum spindles as well for around $800, but they use much smaller rotors.