This may be all wrong, but I think somewhere I read that these bolts were 12/24. It's a little smaller than 1/4"(about 7/32) and much harder to find, but if you're like me and try not to modify things any more than you have to, you'll like knowing this. HF (Or Edsel) liked this thread and used it in several places. Most notably to hold the hood pivot sockets on the cowl and radiator. All 3 of my cars had 10/32s in their place.