Ok to prepare for a Z6 boost application there are quite a few things you need to address. First of course you need your turbo kit. go-autoworks.com sells really nice kits. You will also need bigger injectors. if your looking to run stock internals for now a set of 450cc will do you just fine. Now I see youre looking for 250-350whp, with that being said I would recommend FJ Distributors boost kit. It comes with FJ I-beam rods, ACL bearings, water pump, Vitara pistons, and all gaskets from top to bottom. This kit will hold all you can throw under 400whp. You dont wanna go over that because you'll end up dropping a sleeve. I'll give you a quick list in case I've confused you.
Turbo Kit ~$1000-$3000 depending on what you want
FJ D16Z6 Boost kit ~$600
Fuel Pump (Walbro 255 lph) ~$100
Injectors (450cc for 200whp, 650cc for 400whp) ~$300
4 Puck race clutch (350whp you'll slip anything else) ~$350
Chipped ECU (Xenocron Tuning Solutions does chipping services) ~$100
At least 2.5in Exhaust (Pee shooter wont work lol)~$150
Energy Suspension motor mount inserts (Torque will send your wastegate through the hood, seen it happen) ~$40
After all this, considering it's done correctly, you'll have a reliable DD street beast making 350whp
Hope I helped you out