whats up. man I love my 300ZX. believe me, a well maintained twin turbo engine is good to at least 600HP. Its a strong engine. You just have to keep everything balanced fuel, air, turbos, intercoolers, etc... people routinely get 500+rwhp on stock internals. a great long time established 300ZX forum is twinturbo.net... you should check it out.

Its funny you asked about Hicas because I am putting an elimination kit ($179) on when I do the subframe bushings ($169). Nothing is wrong with the Hicas system but its getting old and you are right, don't want that going out.

To get the car to 500rwhp you will need:

turbos - I paid $2200 for GT600Rs
exhaust manifolds - $950
downpipes - $500
testpipes - $400
injectors - $1000
dual air intakes - $500
ecu - $400
exhaust - probably at least $800, I have borla $1000
boost controller - $300
intercoolers - $1000

I may be missing something in there but those mods will get you to 500rwhp EASY.

you will have to upgrade brakes ($600 at least) and clutch/flywheel($800) with that much power on that car too. stock brakes and clutch can't handle it.

the 300ZXTT just feels great driving it. its low, flat and just fast. I love it. Its a tough car to work on as the motor is crammed in there, so most of my projects end up taking a while, but its fun. Its a great second car, I have no plans to get rid of it any time soon.

I have also had to change a high pressure power steering hose that is a common repair, and its hell to change, so if you look at them check to see if its leaking power steering fluid. I haven't had any major issues in 13 years but I have had alot of minor things that just got old. all the parts are still expensive for that car unless its the rare part shared with some other car (like the starter)

let me know if you have any other questions,

have a great weekend,
Marty

heres a few pics of mine