"sheer bolt" is what you are looking for.
i do not remember the recommendations. for what grade bolt to use. (grade = strength of bolt before it sheers) there is a "code pattern" that you can look up, and then look at the top of the bolt heads. to determine what grade the bolt is.
a local tractor dealer should have various grade bolts, and pending on local hardware store they will offer different size grade bolts.
get something that fits snug. (not needing hammer to drive bolt through) but still snug in the hole. have some extra sheer bolts on hand for when you do sheer them. a bolt that is to loose will "wobble the hole out.
if you can find bolts were you have head of the bolt then a straight piece (no threads), then threads on the end, the straight portion of the shaft might snug up better within given sheer bolt hole.