GQ Towbar bolts!

[Spar]

Hi when I got my GQ the tongue for the towbar was not attached and I am planning on putting it back on. The problem is I have no idea what size the bolts underneath the tail are as they don't seem to match anything I have in the shed. Can anyone tell me what the size and the thread is so I can go down to the fastenings joint and get some high tensile replacements. Thanks heaps!

[threedogs]

It will either be if metric 10mm x 1.25 thread pitch or 12mm x 1.25 pitch.
buy zinc and at least grade 8.
If its imperial it might be 1/2" UNC