Looking For Bolt Size

Hey folks, I have a small problem. Just about finished assembling the 74 Duster but I have somehow lost the bolts that hold the rear bumper brackets to the frame rails. This is the shock absorber type bumper and I need the bolts that hold the inner bumper bracket to the frame. They are pretty good sized but would like to get correct ones rather than some mis-matched out of the bolt bucket. Can anyone give me the specs or point me to a set of them. Thanks A BODY Brothers and sisters.