stock KA's rev up to 6350 or so stock, and i think maybe 6700 or something on s13's (better cams anyways). building something to rev to 8000 would be better on an sr20 or a ca18.

you dont HAVE to build the KA motor. it depends on your power goals really. up to 300whp the stock motor can handle it just fine. granted a few lucky people have gotten up to 350 on the stock motor...thats a little harder to do and would at least need a low mileage or rebuilt (stock rebuild) motor. 350 and above definately needs internals or it wont last long.

if u want some help on it, let us know these things:

-what are your power goals daily? (or what 1/4 times?)
-what are your power goals for 'race day'/max power (those times when you might want to go out on saturday night and plop some race gas in it and turn up the boost for some extra fun)?
-how much can you spend?
-how driveable do you want it? (a decently sized turbo can spool on a stock KA by 3800-4000...a t25/t28 equivalent can spool in the low to mid 2000s)
-room for upgrade?

let us know those and we'll be able to tell you what setup you can go with to get there without breaking the bank, or your motor!