at the bottom is the rb30s
http://www.meggala.com/nissanrb3css.htm

 

RB30 has the same bore as the RB25 and RB26. If you want a real beast slap a RB26 head on the RB30 Series II block. Some slight mods are needed like drilling the head bolt holes on the block to match the rb26 head bolt size but thats it. The block even has the oil and water return holes for a turbo. Not too hard and deff cheaper than a rb26, they may only be able to rev to like 8500 but they put more torque down and make bigger numbers easier. Seen a RB30 make 400rwhp on 12psi then turn it up to 22psi and lay down 800rwhp. Them Australians are pretty crazy.

 

^ your about 4 years late on this convo just to let you know

 

dam lol i didnt even notice that thats crazy well anyway people shud read b4 the type