The bellhousing bolts are 7/16-14, AKA 7/16 Standard thread or 7/16 UNC. Grade 5 bolts should be sufficient, with split lock washers and no flat washers needed. As long as you get 1/2" or slightly more thread engagement after the thread enters the block you'll be good to go. 50-60 ft/lbs. of torque is normal for that size of bolt.
Jerry


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