an rb25 turbo on an rb20 with about 14psi and a re-map of stock ecu will put you in the region of 180-190rwkw.
some have got higher.
and RB25 front cut or just engine even is going to be over $2K to begin with.
Rb25/30 is useless unless you have a larger turbo to go with it.
an RB25 turbo will almost be on boost at just over idle.
so a hiflow or second hard GT turbo of some sort adds another $1K at least.
everyone says (and I used to aswell till I searched for cost of parts and added it up), just get a $100 bottom end, bolt a rb25de head from an R32 to it, bolt your bits and you're done.
but then you realise, oh yeh...
gasket kit - $250
new timing belt - $100
new pulley/idler - $100
new water pump (might as well since the belt is off) - $250
new turbo - $1000
modify intercooler piping for the extra 34mm hight in block - $100
modify the exhaust for the extra height - $100
unless you can do ALL these yourself and have all the right tools to torque the head down correctly, you're looking at about $1000 or more for labour.
then you gotta use your Rb20 AFM and ECU.
AFM will max out quick smart.
ECu will need to be re-mapped or replaced with PFC or similar.
might aswell get the Z32 AFM.
there goes another $1800 (rb20 PFC is rare and still around $1500)
then tuning will be about $500 minimum
then you have your car running.
and damn it goes alright..
then, bang.. rattle rattle, crunch, crunch..
oh there goes the glass RB20 gearbox.
let's pull together $1500 for an Rb25 box.
hmm.. clutch could do with a refresh..
not to mention the flywheel.
$400 RB20
$300 rb25 turbo
$500 to get it in the car with new belts etc.
problem solved.