I believe the bolt is either 1/2" or 9/16", fine thread, 18 threads per inch. I am not certain of the grade. They are original wheel lug bolts that appear to be in excellent condition. Your link provides great information. Thanks so much! Based on your link it appears 122 to 172 would be acceptable. I prefer to yield to caution and possibly torque to a max of 90, as suggested, and check them regularly.