you may want to try out @Nothern Garage in Sg. Ara ... the boss is very friendly and the price is very reasonable too (don't get scare off with some evos or wrx in the workshop)
Nissan never actually produced an RB30 with the Double Over Head Cam (DOHC) cylinder head for SKYLINE SILVIA or FAIRLADY. The RB30 block was produced by Nissan for the Holden company...