Anyone know the thread size and length of the engine mount upper bracket bolts? I should have noted this when I had them out, but unfortunately did not.

I'd like to buy a new bolt with a thicker head to replace the left top front bolt that I couldn't get quite snugged up because the socket kept slipping off - I figure I have a better chance to get a new one tightened to spec. if the 13mm socket will stay on the head better.