HELP PLEASE: wat size bolts go where?

just wondering wat size bolts go in the rear bumper support brackets on an oval and wat size bolts hold the back seat into the walls as i seem to be missing a few bolts here and there since the rebuild and would like to purchase some new ones of the right size. will think of more i need as i find wats missing... thanks
sam

This is where the 'bucket 'o' bolts' comes in handy.

my bucket o bolts is nearly empty and nothing seems to fit the remaining holes.