Z400 hubs fit, and you can bolt Yfz450 calipers to those.
Honda 450R and a Yfz450 master cylinder also work/have the same thread pitch. The Ltr 450 mc may/may not fit, as I'm unsure of the thread pitch on it.
The Z400 hubs require new wheels though, as they are a different bolt patternn than the 500. There are alot of aftermarket wheels available that fit multiple brands, not just the Z400. It's a common size.
SS brake lines of standard length may work as long as you have stock a-arms.
Sorry, I don't know what(if anything)will work to replace the rear brake.