Transmission Bolt Size

I've discovered all the bolts between my bellhousing and transmission have fallen out. Can anyone tell me what size those bolts should be? I'm guessing they are Metric. I'm about to go buy a selection and start trying.

IIRC

It should be M12 x 1.75thread @ ~45mm length with a 15mm head.

I've read somewhere that some parts suppliers use an 18mm head on that size bolt, and it will cause intallation trouble since the socket is harder to fit.

it's been a while, but i believe they have a 13mm head.

Thanks for the help guys.