There are several stroker kit options for the RB30 block in much the same way that the RB26 has a wide range of options that can increase its displacement from 2.6 to 2.7 (Jun & Greddy), 2.8 (Tomei, HKS etc), 2.9 (BC) and so on. The RB30 has RB31 (OSG), RB32 and RB34 (both stroker kits offered by Spool) however besides the OSG which is more of a race oriented setup, the rest have yet to be proven in the long run. I'm sure there are people out there running RB32s and RB34s with success however the number of users would be dwarfed by those successfully running RB30s with good, reliable power.
Too bad that R34 isn't a GTR or are my eyes failing me as I age ever so gracefully?