The ’47 panel truck bed wood has a strip across the rear that is held on with 10 bolts. From what I have found these bolts are called Countersunk carriage bolts aka 114 deg countersunk square neck bolts aka Flat square neck plow bolts. This is a ¼” bolt maybe ¼-20, and about 1 ¼” long. I’m missing one and another is bent. I have found some on-line that don’t match the dimensions, so I’ll go to the local fastener supply places next. I thought someone here might have a source. Thanks.
