Factory Spring And Shackle Bolt Grade

I need to buy some more to get this thing back together. The bolts I have (likely factory) are marked with nothing but a triangle. What grade were they supposed to be? I wish the tsm listed more than torque specs for this stuff, but I'm being picky.

I could go grade 8 and forget about it, but theoretically if I were to get hit or something I'd rather break a bolt than transfer all that stress into the frame.

 

I strongly recommend grade 8 for all applications. Grade 5 exists to save money vs grade 8. And Id rather bend a frame than have my axle go on independent ops (which will then probably bend the frame anyhow).