I did a search and never saw this question answered, the stainless kits come in button/socket head (both are alan head) or hex phillips head neither seems totality correct. which one have you tried or would be the most correct?

 

For what piece? Bed wood? Fenders?

 

At bodyboltkit.com they have 6 different heads to chose from.

Shoot, I just looked closer, the dropdown list doesn't give you all 6 options. It varies from kit to kit. Well that sucks.
I wonder how much different the 48 - 50 kits are from the 53 - 56 kits. They com in the Indented Hex style...