Just how much would you like to spend?
You can keep you bike stock and convert it to a track bike with a few mods..
You can save a lot of weight by taking off the oem fairing all the lights/signals/meters and fitting only fiberglass top fairing/tail/tank cover.
APE offers also a plastic gas tank that is a lot lighter than oem.
But like said here earlyer it is better to get a salvage busa and mod it.
Again only fiberglass top fairing/tail/tank cover,no wires except the necesery for ignition,no lights instruments,no battery(APE also offers a engine starter engine cover) no pair system
no starter motor and ballancer.
You can cut the pillion part of the subframe and get a pair of ebay yokes and loose the heavy stock ones.
And fit what ever swingarm is sorter than the busas' for a a shorter wheelbase..