If I wanted to purchase new hubs that would directly fit the Brembo rear calipers and rotors from an STi, I would need to use 5x100 STi hubs from a 2004 STi or JDM variant that was also 5x100 (just for wheel fitment because I've heard strut mounting is the same for the rears.). Since all STi's used R180 rear ends, this would force me to upgrade my rear end and axles, or else the stock axles I have wouldn't fit into the spline of the new hubs. I'm okay with that because I want to upgrade to the R180 anyway.

Comparing axle lengths on RockAuto.com between the 1999 Legacy and a '04-'07 STi, it seems that the length is a little off, not allowing me to use off-the-shelf WRX STi parts. Does anyone know what I could use? Watching the Gramps build on MCM, they don't really even mention the axle change requirement. In fact, they hardly mention anything regarding the particulars of that swap.

So, do I just use R180 STi axles?