std stroke and bore RB26, stock springs, 9.15mm poncams, 34psi making 467kw at the tyres...HKS 2530's.
no need for anything bigger than this on a low revving RB30. Throw some springs at it if you feel the need though.
i don't think that camshafts or springs (unless they are faulty) are holding you as far back as you are now.