Chevs of the 40s now sells these bolt in a set.

Classic Parts sells these - they are not like the original bolt. They used to sell a bolt like the original but it was quite expensive. You should use new clips

Jim Carter still sells the original style bolt and it is appropriately expensive. He will probably stop selling it because people are will to buy the cheaper style. locking clips

As Classic Parts states, use a thread locker compound and a lock plate to assure the bolt will not come loose.