No Loctite please! The objective is to prevent the threads from seizing. Loctite, in effect, seizes the threads. Hypoid gear oil, or moly paste as an alternative to anti-seize.

Absent Marie Antoinette, we might well ask how the bolt came to lose its head. The most likely scenario, to my mind, is that the threaded hole in the block, being a blind hole, has a considerable amount of dirt/rust/oil accumulated at its bottom, preventing the screw from being run in for its full length. When the screw was stopped before the head was in contact with the bearing tower, additional, excessive, torque was applied until the head of the screw was twisted from the shank.
An alternate scenario has a bolt from an aluminum block engine being substituted for the original. The bolt from the aluminum engine is longer, and would bottom before the bolt head was seated. The underhead length of the wrong bolt would be 165mm. Measure the recovered, broken part.