My name is Saif and i have atuning shop, i'm from U A E , i have worked on many RB26DETT engine, i think i can help you building yours
1) Pistons : HKS, J E , or ROss, (( go with ROSS , i can help you with the part number ) , cost : $700
2) RODs, Crower ( cheap and good ) Also i can give you the part number , Cost : $950
3) Nismo Crank main bearings, Conrods bearings , Cost complete sets : $130
4) Cams , go with HKS Step 2 , ( two Cams + 24 Springs + Two Cam Pully ) you can safe alot of money, cost $ 950
5) Metal head gasket : 1.2 or 1.6 , cost : $270
6) Oil Pump , I liked Trust , but you can go with Jun , HKS or Nismo, Turst Oil pump may cost you $800
7) Trust Oil Pan , cost : $240
8) for the Turbo kit, HKS T51R Kai is the best kit for the GTR , cost price : $4800 ( Complete kit with down pipe )
9) HKS Intercooler type R, cost $1600
10) ORC twin or triple plate clutch , cost $1750
11) HKS Fuel Rail
12) HKS or Sard 1000cc injectors
13) FC power and commander
14) HKS exhasut system
15) Fuel Pump, you can add nimo intank fuel pump ( cost $300 ) , and if you want to save money , buy Toyota Supra turbo Fuel pump .
16) Trust Oil cooler
This is all
if you need any help let me know and if you need any parts from Japan , i can help getting parts direct from Japan ( 10% to 15% cheaper than Takakaira )
good luck