Flywheel teeth broken Tecumseh H70 engine on 1977 Ariens

Have an Ariens ST724 model 924032-008001. 1977. Snowblower
Has Tecumseh H70, model 1302100 SnowKing engine.
The flywheel has 18 broken teeth, so I need to find the correct one and a bit of "DIY, how to do the change."
I found numbers, (if correct?) 30811A Flywheel, and a 6111085 Flywheel (more than half the new cost of the machine in 77!) I do not know difference between them. Maybe should go for a used one if available?? (guess check see if magnets still make it work?) NO headlight on the Ariens.
Also, the engine shroud must come off, but two bolts on the engine lift ring, are they head bolts, or just bolts. Will that be an issue? When removing shroud? Any guidance on doing this repair would be helpful Thanks
Thanks I am stuck and too old to hand pull the engine.
ron3033