Well the ca vs ka debate is not exactly a toss up. The KA has a longer stroke, weaker rods and higher compression whereas the Ca has a short stroke and oil squirters and is turbo friendly from the start. Ka's seem to grenade past 12psi on stock internals whereas I have seem CA's reliably push 20+psi on stock components. (in fact, the upper limit of the CA has yet to be tested in the states) As far as mods, all you need is a larger turbo, injectors and some sort of fuel management. All of these parts are readily available for the CA and a lot of SR parts are directly interchangeable with the CA including intercoolers and exhausts. Also, all gaskets and anything oem are identical to the 1988 Nissan Pulsar NX SE so replacement parts can be found at your local autozone just like KA parts. The only place I see the KA having a real advantage over the CA is in it's displacement and the fact that it is already in the car. The torque curve on the KA is ridiculous and it responds very well at low boost. So in my opinion, if you have a KA in good shape and are wanting low boost 7-10psi, go KA-T and you will have a torque monster that is a blast to drive. I originally chose the CA as my KA was blown and the CA had a lot of advantages over the SR as far as strength and price (for the motor and for parts). With that said I have seen a lot of KA-T's die in this area before my untouched CA offered the slightest hiccup.

But I think the general idea is to just pick something and build from there. All of the Nissan motors have their advantages and disadvantages with the common theme being that they are all a pain in the *** at one point or another.