There are some conflicting bits of information about your request.
Dash bracket to the dash - the book says 356780-S2 bolt, 5/16-18X3/4 pan head but I find nothing confirming this. I've found 378178-S2 bolt, 5/16-18X1.0 hex, disc (the same bolt used on the fenders) and 55736-S2 nut, 5/16-18 hex serrated (the same nut used in the spring shield, aka upper A-arm bumper bracket) used there.
Dash bracket to the firewall - 378735-S2 bolt, 5/16-18X3/4 hex, disc (a shorter version of 378178-S2), or I've found 378178-S2 itself, no separate nut, the bolt goes to a threaded insert.
Rear axle bumper - the book says 41196-S8 5/16-18X5/8 hex thread cutting.
AMK carries separately 378178-S2 and 55736-S2, I could not find a kit. There's a kit of 2 for 41196-S8 as F-1486. I don't know what comes in this kit. Head making will most likely not be as original.
Jim