Re: Broken bolts
If you drill, it is critical that you drill very carefully, and be certain the initial drill is centered in the broken off bolt. I think the block is likely aluminum, and those threads can be easily wrecked by a wandering drill.
Can you face the end of the bolt with a file or small grinder to make it as flat as possible, then use a punch to be sure your drill starts in the center? If you get a good starter hole, soak for a day or two with penetrating oil or home brew to increase the odds of it breaking loose if and when you try the easy out.
In all cases, don't be in a rush. Take your time and be very deliberate with the drill.
X 500 48" Deck 48" blade
Stihl BR 600
Sears Suburban Super 12 1968
Craftsman 1990 something LG Tractor 46" deck
Original Kohler 8hp Giant Vac early 1960s