Search Ebay for "plow bolts". They're a sort of modified carriage bolt with a tapered head, and they're available in various sizes, lenghts, and thread pitches. Either cross-drill the bolts for cotter pins and use castle nuts, or use Nylock nuts without cotter pins.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!