I couldn't find them either.
From what I have read at other websites, some are using stainless Torx flathead bolts.
The reason being, removing the old bolts with the square on the neck simply spin in old wood (no grip).
Have to grind the bolt off from the bottom of the bed.
If you want the look of original, find someone who is good with a lathe and have at least 10 of them so they look the same.

"Adding CFM to a truck will only help at engine speeds you don't want to use."
"I found there was nothing to gain beyond 400 CFM."