Turbo charging a Toyota 86 some advise needed please.

I recently bought 2013 Toyota GT86 as a project car, I decided on this platform because there is so much available for this car and I think this will help me in gaining experience and keep costs down.

My plan for the car is to build a really fast street car that I can use at track days.

I plan to fit a turbo and I’m definitely going to have many questions along the way.

I do plan on building the engine and upgrading the internals with forged quality parts long term but will need to do in stages as finances allow. My first step will be installing the turbo kit to the stock engine and sorting out any teething problems.

Once I get to building the engine my target is to achieve around 450HP and around 1.2 bar boost on pump gas and 1.6 bar on ethanol

I do have some questions already and need some advise.

How far can you safely push the stock engine in terms of boost and HP?

Apart from forged internals(pistons,rods,bolts) is it advisable to upgrade the valve springs for the power and boost I am targeting? Head gaskets- are the stock gaskets good enough and what are the alternatives recommended?

I have decided to go with a Garrett G25 550 turbo but Im not sure what turbine housing to use the 0.72 or 0.92. My thoughts are to go with the 0.92 housing so the power doesn’t drop off at the top, but unsure? I was also considering the G25 660 and using the 0.72 turbine housing. I do want to maintain good drivability. Any advice will be much appreciated please.

Thanks

We were making around 330-340 whp on a stock engine with an EFR6758 for about 3 years with great reliability on E85. To get to 450 hp I'd suggest pistons, rods, valve springs, HKS head gaskets and possibly an ARP head stud kit. The G25 550 would probably be a pretty reasonable choice. It's a little hard to advise on the exhaust A/R - the 0.92 will make more high rpm power but you'll sacrifice response. Personally for a street car I'd prefer the response and a little less power. Bear in mind that you'll destroy 4th gear with anything like that sort of power.

Thank you @Andre.Simon