James, the guy who owned the 185 we used for part of a summer had the original wheels and brakes that Cessna used, McCauley, if memory serves. Anyway, he had one of the brake pads get loose, which is common on those. Luckily, he was landing on the grass and it didn't ground loop. Ordered up the new Clevelands and asked for 6 bolt wheels. They said that wheel was not approved for the 185 and wouldn't sell them to him. So, he got three bolt. As it turns out, the 6 bolt wheels use smaller bolts.
There is an air taxi here that runs 2 206's and a 207. He and his pilots are shearing bolts all the time, really honking on the binders to make the turn - off...you know the story. They use 3 bolt wheels. I don't think it is legal to drill them, or he would have done it. Might check with one of the Maintenance Inspectors.