dont bother, ther is plenty aftermarket rods availble for the RB30 and would be much better than a chevy rod,
they are based on chev rods in the sence they have used similar technologies to produce them. ie forged "H" beams instead of cast "I" beams for instance.
But the Nissan RD28 diesel has a visually similar rod, I have noticed them at work a few time when i was builing a VL some years ago but never acctually compared them for size, that would be much more heavier duty than standard if you a looking for a cheap and nasty way out.