sorry man, i really, really, really disagree with a 5k being "worth it"
i put a 5k into a ke35 i had a year or so ago, and it sucked. 10% more powerfull than sweet f@$kall in complete honesty. you see people with decked out 5k's and they make bugger all power, and would never, ever be able to compete with a 4age, let alone a 4agze.
i gots the 4agze now and its good. i beat kids in s13's, s14's and s15's. i beat a kid in a rb25det cefiro and many many commodores. then i killed the motor. haha.
but yeah.
5k swap took a weekend. 4agze swap is not so easy.
still, i'd rather spend 6 months to put a DECENT motor in that you'll enjoy. trust me mate, you'll love it when your car is running.