The bottom bolt is threaded into the block. If a longer bolt does not fix the issue, the you can legally use a thread repair per Briggs rules. If it was any of the other 3 valve cover bolt holes, you would need to replace the rocker plate. Either way the head does not need to be replaced. Also, don't over torque those bolts. 125 inch pounds is plenty and will not destroy the threads.
16. Cooling Shrouds, Covers and Blower Housings
All pieces of the engine cooling shroud/blower housing and control panel must
be stock B&S and properly installed. Rewind housing and cooling shroud (air
guard) must remain stock as painted from the factory.
Engine Shroud may be painted any color. Any bolt, with the exception of the head bolt, that is used to secure sheet metal shrouds and covers may be replaced with larger diameter bolts.
No taping, covering, or restricting of air to the rewind shroud is permitted