I'm 99% sure they will fit ok, but know 100% the xr4i calipers/discs fit, these are 260mm, same size as used on series 2 rst.
You will need at least 14" for the 260mm discs, I think you need 15" for the 273mm granny ones.
Better pads make a awsome difference, try some ebc yellowstuff, or redstuff.
tabetha