66 fury foot throttle linkage

[66furys]

I have found something interesting recently. My throttle cable runs thru a floor plate, that was moving around a bit. Someone, for some unknown reason removed the two small bolts, that have weld nuts on the plate, and come in from the firewall.....all gonium. So, I thought I might have my small hand partner install the bolts, but real tight behind the engine. So then wanted to find the size. There is NO possibility of a 1/4 SAE....too big. So began to look A 6mm bolt works. Went thru one side by hand, and half way on the other. After running a tap, the new 6mm bolts are in and tight. There is NO SAE fastener (or USS) that is close to this size. What in the world??