Ace hardware has always had the best selection of bolts anytime in needed it. I think most of my cars have had a bolt from there at some point. They have flanged bolts so get a grade 10.9 M16 and you should be good to go.

 

Thanks everyone and thank you greisinb for that video link. I learned a lot from it.

I ordered one of the RYG501550 (ANR5804) bolts from Atlantic British. When it gets here I plan to take it to a near by Fastenal location and see if they can give me all the specs on it, as well as if they have a longer version.

Once I get this diff guard mounted I'll post a picture here. Thanks again.

 

Any more info on the guard though? Looks pretty cool.

 

Second the McMaster Carr site. I have spent way too much on good quality stainless steel replacing a lot my rusted bolts. This forum should get a kickback. For your current need you will want a good quality steel which is less expensive and stronger, which the site details.