Ah great, another GTR being built for hills. The ONLY reason i still have mine is the fun it can be on the right hills
Ive done a lot (days and days worth) of thinking about what would be unbeatable up hill runs, here are my thoughts;
-Full built RB2630 with stock crank, mild ported head, no bigger than 270deg cams, 2860-7's,
-Full built RB2630 with stock crank, heavily ported head, 270deg huge lift cams, 2860-5's
-Full built RB2630 with stock crank, mild ported head, 260deg cams with huge lift, R34 N1's
Id imagine any of those would be uncatchable.
To answer your question though, i would suggest 2860-5's instead of the -10's. There's plenty of street GTR's (2.6L) using the -5's and seeing some pretty great results. Ive been in a couple with the -5's and they haul ass in a big way. Yes the -10's will give you higher numbers but the thing is, if you're going after 500hp at the treads just for mountain runs there's no point having unrequired lag on your way to 500hp.
Id be going;
-Mild head porting
-Tomei 260 10.8mm lift cams
-Tomei buckets
-Tomei springs
-Stock exhaust manifolds port matched and ceramic coated
-Tomei dumps ceramic coated
-Ceramic coated front pipes (whatever brand, just good flowing)
-Dash 5's
-9.0:1 CR or higher
plus all the usual shit