Good luck. There are screw extractors that have a left hand twist to them. You drill a hole, and insert the extractor in a left hand direction. To find strong bolts, look at the head. The more marks on them, the stronger they are. The really good ones have a mark that makes a hexagon or such.
Driving over and over the lawn seems like a lot of work. I had a bagger but it broke. It was a lot of work, too. I think I will look into blowing all the leaves and clippings (once they are dry) into the four corners of the yard. Once there I will add compost starter and spray the piles with...
just got mine going. The little hose from the valve cover to the fuel pump had a crack in it. Taped and glued the crack, and it runs now. If you remove the valve cover to fix or replace the hose, notice that the valve cover will need to have a sealant applied.
If your Pony has the variable pulley between the motor and the rear end, check to see if it spins freely. I just found the bearings on mine have gone bad, seized. $20 each, takes 2. Check belts while it's apart.