This is a Turbo or Series II block
Besides the feed / return lines I am unaware of any other differences between a Series I and Series II block.
I believe the Turbo block used a higher flow oil pump but not 100% sure.
I also believe that the pistons in a turbo block have a dish, again, not 100% sure.
I wish I knew a place that sold cheap rb30's here! Every wreckers I go to wants over $300!!!
Feel like selling some N1GTR? lol