Mate did 350rwkw as follows:
rb30 block $100
Forged pistons $1400
Machining + head service $1000
Cams $1400
GT3540 700hp $1800
Tial wastegate $550
Injectors $1200
EMS Stinger $1100
ARP Rod bolts $???
Plus obviously gaskets, bearings,timing belt, intercooler, tuning and the big part, labour if you don't do it yourself.
The standard manifolds are capable at that power, just need to weld a wastegate on top.