Brake lines and vent lines are attached to the chassis through use of a 3/8-16 self threading bolt. The NSN associated with this is 5305-01-236-4349 . The manufacturer part number for this is 172482.
This bolt is called out a number of times in the parts book, and in at least one place it is referred to as: SCREW, TAPPING 3/8-16 X .62. It is primarily used to hold down brake line and vent line loop clamps, and is even used on each hub to attach the vent line loop clamp to the hub.
There really isn’t an easy substitute that looks or works correctly on this. We found at least once on the 1038 where a mechanic (or other person) tried threading a 3/8-16 bolt into the frame to hold a cushion clamp on, but it simply would not tighten.
We have ordered these screws from some of the “big 3,” and they worked, although they seemed to be a bit longer than the call out. And after we acquired a bag of 100 of the proper screw (with the proper NSN), it was noted that the ones ordered from one of the “big 3” were slightly longer.
As these screws range from $0.16 to $0.25 per screw, we recommend using the correct screw as called out by the manufacturer. Because of its low price, the damage that could be caused by using an incorrect screw would far exceed the cost of using the correct fastener.