well theres another problem

people are idiots.

see, nissan did NOT cram 6 gears into the space they had with 5 gears.
it's a totally different transmission casing size and everything and different part number entirely.
the S15 trannies have problems with the input shaft teeth shearing off. what's the deal with that ? it's not the thickness of the gears the problem, it just happens. T5's do that all the time also.

As of right now i dont have a bellhousing that will work with a KA and the nissan 6 speed. and you can't interchange the gears either.

I suggest changing out your final drive to a 3.70 if you want 3000 rpm to be 80 mph in 5th gear.