thermostat bolt stripped

Recently purchases a series 3 2.25 Diesel (1977) and when cleaning up the engine bay the leak from the thermostat was because one of the bolts has stripped... has any one used loctite thread repair or will i have to re thread...(have tried to rethread the same size but the bolt still pulls..don't really want to go a size up if i ccan help it

thanks

There must be some issues, not only double posting posts, it’s repeating threads too.