Water pump bolts

Apologies if this is in the wrong section

But does anyone know what type (size and width) this bolt is?

Changing the alternator bracket on the small block dart. Top bolt came off no problems bottom one (the one circled) took much more persuading spinning around and around. Infact it got stuck 80% of the way out and needed some tapping with a hammer and chisel to get it to budge.

Now when I go to put it back in it just slides back and forth with in the hole As if it's not long enough or wide enough to catch the thread, so now I'm wondering if its even the correct bolt and not a bodged fill it with sealent and slide anything in type affair.

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