does a square peg fit into a round hole?

[TRAU 82]

hows it going guys...sure i'm not the first one to ask and prob wont be the last, but got a question hoping you guys can shed some light. is there any good/better way to repair any of the square holes in the bed of our trucks for the carriage head bolts that may have gotten rounded out when removing the bed for the first time? tried like hell to keep it from happening, but when 2 or 3 started rounding out and spinning in place, i broke out the grinder and had to grind off every head!! any advice you guys can offer will be much appreciated...