Replacement Bolts Question

[71beast]

Hey guys, was hoping someone would know both the bolt size and thread pattern for some of the bolts in the engine bay of a 1971 Chevelle. I've checked all my manuals, but no dice, and I really don't want to just take all them out to match them. I'm not looking to get a kit, because I'm looking at changing a lot of the bolts to stainless and someone of them need to be buttonheads for more clearance.



I've put some arrows for all the bolts I was thinking of, but if there are others please let me know. For some reason I think they're all 5/16"-18, but I have no idea of lengths. Oh, and I need to know the size of the bolts that hold the bumper from underneath, as well as the bumper brackets. Will be nice to change them once and never have to worry about them again . Thanks guys.