Crank bolt to hold damper

Going up a size is the best repair. But, I would not be looking forward to drilling and tapping the crank snout by hand. At least the motor is out of the car. Drilling straight shouldn't be too bad, but hand tapping that size and getting it straight is not going to be fall down easy in-situ. If you do try to go up a size, you probably want to use the NF thread for that size. The original used a fine thread for a reason, and I think it might be easier to tap the fine thread. if you can get the damper off, you may be able to cobble a tap guide out of PVC or something to slip over the snout and keep the tap somewhat straight. Depends on what you have available to you.