I found some 8" (6" would be long enough) long 3/4 " dia grade 8 bolts, with threads only a short way up the bolts that fit the jack holes just right. May be ok for supporting on jack stands, but not good for jacking with a trolly jack. This is because the the angle of the jacking hole is downward. Don't go with less than grade 8 and stay clear from pipes that could bend. It never hurts to put additional jack stands under the car, even if they are under more vulnerable spots as a secondary safety net. I'd rather damage the car than myself if something went wrong.