I'm glad that Gumbrick posted up about this. I did 54C main bolts on my last motor as they're a lot stronger and cheap. You don't hear hardly anything about mains bolt failures, but it's hard to justify not spending $20-40 on some bolts when it's so small compared to the rest of a rebuild cost. BTW, 54C mains have also been referred to as Nismo mains.

Lets face it. The bottom end on these motors is pretty damn strong. Do whatever you prefer, because it would really only make a difference on about 3-4 of the local motors around here.