Kz750b engine mount bolt size question

Brought an old bike back to life recently. Apparently at some point a previous owner decided the Lower most mounting bolts weren't needed. I'd like to replace them. What size bolts should be used? 

My manual lists torques but not size. 

M10 x 325mm. your best bet is to buy some all thread or solid rod and cut threads, then use a nut on both sides. I oversized all the engine mounts on my 750 to 7/16" to remove factory slop and use a nut on each end.

Partzilla sez....

10 X 325

See reference number 41
www.partzilla.com/product/kawasaki/92001...4439ab444fbee2a48a11

So 325mm long? That should be something just shy of 13in. Is this supposed to be a single bolt that goes from side to side and not two sperate bolts?

If so I can see why all thread would make for a good solution. 

Before buying new bolts, be mindful of the size of the bolt heads & nuts. If too big, they may not fit, especially in the engine case channels.