2 questions on the case cover for a 2010 MB HD45 Mag.
-Are all bolts in the cover the same size? I had one fall out and want to make sure it's ok to just pull another one out and match it
-Is the general consensus that for a leaky cover it's best to replace with the vanguard gasket or use something like yamabond in lieu of the gasket?

The general consensus is that there is no general consensus. Do some searching on the forum. We've discussed this a LOT, and the latest that people are content with involves a bit of machining and yamabond type sealant, which is what Briggs is doing from the factory now.

I've read every thread I can find on the subject so I've definitely done my research. Just seemed like there was a lot of conflicting answers.

That's the point I'm making. Pick one, do it right, and roll. The important aspect to all is torque bolts to spec, check them often, and wait for it to leak again. Some don't, but plenty will, regardless of what you do. We all have a different opinion on what we prefer to close them up with.

10-4. Thanks for the help. Any insight on the bolt sizes?

Put a 8M -1.25 stud in block with some lock tite and put a Nyloc nut on it. See if it comes out again. I replaced all the bolts in my block with studs and used Nyloc nuts on them, and never had a stud or nut work loose again. Also no leaks after 80 hrs.