i run that same (looking) trx250r shock on my black bike, at almost 17", it will not work on a stock swingarm without relocating the bottom shock mount. (unless you like the trailer park airshock camaro look ?)
the KOR 400ex bushings do work for the smaller diameter bolt, but need mounted on the outside of the frame mounts, and the shock bushing shaved down to fit between the mounts
when first installed on the +4 swinger, it raised my grab bar 6" higher than normal, thats unexceptable.
i relocated the shock mount back and lowered it back down to 1" above normal.
i do really like the longer travel and plushness of those shocks and is well worth doing what is needed to make it work