the two housing options that I have right now are this:
1) T3 5 Bolt (ford/wrx/evo style) turbine housing that is .58 A/R
so coming from the turbo manifold its a T3 connection, and going to your downpipe its a 5 bolt connection
that a standard A/R, should net around 400-450 on a KA depending on internal mods. I've seen a friend of mine hit 475 in the useable spectrum but he had a fully built head.
2) T4 3 inch V-band turbine housing that is .82 A/R (with an optional adapter that goes from V-band to the GT T4 4 bolt downpipe connector)
so coming from the turbo manifold its a T4 connection, and going to your downpipe you have the option of a 3 inch v-band connection or a GT T4 4-bolt connection (essentially a 4-bolt that has a 3 inch internal diameter)
this is more for a track or drag based powerband. it will hit much higher hp #s (between 475 and 600, depending on engine mods) but it will be later in the powerband. usually more along the lines of a drag racer or big open course
race where you can keep it up in the higher rpm most of the day.
any other questions feel free to let me know.