For 300whp you dont really have to build the engine at all, you can just get a new oem water pump, new oem oil pump, and then get some bigger injectors 550cc and a garretty gt2871r with the .64 a/r. Then find the standalone EMS you want to use and put it on the dyno.
For more than 300whp, start goin with ARP Main bolts, Eagle or Carillo rods, you can choose from JE, Wiseco, CP and Arias pistons, a metal headgasket (Apex'i, greddy, hks, tomei), Might want to think about going solid pivot head instead of hydraulic so that the lifters dont start coming out at higher rpms even though rocker arm stoppers can prevent that, but have not always been able to. HKS Step 2 cams or Tomei Procams, titanium valve springs and retainers, more than 550cc injectors if your going to start pushing over 350whp, if your going to go over 400whp, you might want to forget about trying to get a minimal lag turbo, since most the turbos at that point start coming on to hard power at about 4k rpm, but if the head is built and the bottom end is as well then you can probably rev to about 8500rpm+.