Today I got the new right angle attachment, bored out the hole to 3/8 inch and used a tap powered by a 7mm small wrench to re-cut the threads to 7/16X14 and after a few tries cut them through enough to insert the too long bolt I bought at Tractor Supply. Then I decided to clean the threads in an inconspicuous place - beneath the batter holder – and use the long bolt there instead. That way the visible bolt will be original. It seems the head of the bolt is larger than the new one I bought although both are 7/16 inchX14. Now it seems the depth of the cut threads in the location under the battery is less than the length of the bolt so I can either cut the threads further or cut off the bolt – maybe. I have an air cut off tool and three inch disks and so will give it a try since I bought two of those bolts so one could be a spare. Anyway, I got tired so decided to come in the house and rest. I believe I have some moly grease which I can put onto the threads of the bolts before putting them back in the engine and hopefully keep them from seizing again. It is progress. I also used a die to re-cut or refresh the threads on two of the bolts and will do the rest before putting them back. It just makes sense to me. I may also refresh the holes if I can get to them easily. I do need to find a leather glove as that small wrench hurts my hand now. It takes quite a bit of time to do this re-cutting yet it seems a good thing to do.
Only God knows what was on the bolt that broke off as I never did get it out. For practical purposes that no longer matters. I will be changing the oil for sure as there are steel pieces in the engine area from all the drilling and filing I have done. No one on earth knows when the oil was last changed on that engine since the man I bought it from did not do such things.
Tractor Boy