what are good t3 specs

[IH8TEC]

ok i'm in america for a while and i've been looking on ebay.com at turbo parts for my gtz.

specifically i've been looking at the huge amount of t3's they have on there, quite cheap really. what i was wondering is because i'm not that clued up on trim, a/r etc etc. what would suit my application, i'd what boost hard from about 3500-4000 - redline, be able to flow about 20-22psi, not that i'd run that high, FOR NOW.

like i notice some have .60 or .48 etc, what are all these numbers, which wouldbe best,

also i notice that some are oil cooled or water cooled or both, which is more ideal cheaper to install etc.

cheers
brendon