there are series 1 and series 2 rb30 blocks. Series 1 has the blanked off casting marks for the oil and water feed/returns. Series 2 has the same oil and water feed/returns except they are tapped and have bungs in them. So yes you are chasing a series 2 block with the bunged off holes. When inspecting a block..just look on the exhaust side for the oil return, oil feed and water return in roughly the same spots as your rb25. Piece of cake to find mate. If its got the bungs, it the one you want So long as the motor is in half descent condition.
haha we bought 4 rb30e's outta vls from various places when we built the latest 25/30...they arent all in good condition.