maybe i'll just buy a new fukn car!
well, with modifying cars, a lot of people just dont understand how expensive it is. everything involves money, and nothing comes cheap. people with the ca20e powered pintaras are extremely lucky with the fact that the can keep their existing mounts & gearbox & stick a ca18det in. they are a powerful (and very underrated) engine which can make more than enough power to satisfy your need for speed.
unless you can get a ka24e and all the equipment required to run it (loom, ecu, gearbox etc) for cheap, then its not a mod swap worth doing for ca20e owners. you'd need engine mounts from a 2.4 litre pintara as well. and all that effort for another 13kw. definately not worth it. fair enough, sssgtr is getting big power out of his ka24e, and the american 240sx owners (forget about most of the stanza owners other than sudesh) are getting big figures from their 2.4 litre engines too. however, it still costs a fair bit of money to get your engine to that level, expecially if you dont want to, or arent confident with doing a bulk of the work yourself.
an engine swap can be performed by yourself in the back yard succesfully in a weekend. it happens all over australia. every weeekend. someone is swapping an engine. its just a matter of time and money. you have to ask yourself, do you want to spend a little bit of money on your car, a car which you already know & can trust, and having loads of fun slaughtering v8's & the likes, or, do you want to fork out nearly $10k on another 2nd hand car and quite possibly, have picked up a complete lemon that is going to cause more trouble than its worth?
in the end, you dont have to swap the engine just because its hit 300,000km. is there even anything wrong with it? if there is, and its internal & not easily repairable, get it rebuilt. while its getting rebuilt, have the head ported & polished, put in a performance cam, fit extractors and an exhaust, and then get a chip tuned to suit all these mods. it will still cost a bit of money, and will never compare to a ca18det or sr20det, but it will be less hassle for you, and, most of it can be done in parts, so you dont have to have the entire sum of money up front (like for the engine)
so, save a few dollars here and there, and get yourself a good 2.25" exhaust. it should only cost around $100 for piping + the cost of your muffler, no resonators, it'll be nice & loud and you'll feel a bit of a pick up in power. and if you decide to go ca18det, you'll need a bigger exhaust anyway. this is all of course, assuming you dont already have an exhaust. if you do. save up for a CAI and buy a pod (good simota pods are $40 plus $20 for an adaptor) a really good CAI which locates the pod outside the engine bay will set you back about $300-400 for mandrel bent pipes.
anyway, after all this. in the end, i'm just saying, decide what you want to do, or if you need/want a swap that badly. if you do, you'll find a way to get the money. but just be prepared to spend it. if you dogo a turbo swap, you'll be grinning ear to ear for years to come.