In a standard M*G, a couple things are against us. The pedestal has play within the switch assembly.
What you MIGHT be up against is that the filament height on the 1160 is higher than the reflector can handle. You MIGHT need to cut a bit off the legs of the bulb to get it down there.
The clue would be, when trying to focus sharply, the beam doesn't quite get there before opening up again.
I have a couple stock MC bulbs being driven by 6 cells in a couple lights and I HATED it the first time I installed one. But after adjusting the bulb (with Bipins it's EASY!) I am quite pleased with the results!
Good luck!