I drilled out my Simpson D3s with a C clamp, a cordless drill, and a small round hand file. With patience and beer, anything is possible. It probably took 15 to 20 mins per hole, flipping the bracket over repeatedly to soften the metal lip that forms on the centerline from drilling each side of the hole, (you never really punch through). Then I used the round hand file to flatten that centerline and kept test fitting the bolt until it pushed through and fit like a glove.
Using a cordless drill eliminated any opportunity for me to lose my cool and overheat the bracket and cook the belt, so I'm thankful for that. As easy as it was to uninstall the old belts, it only made sense that install would be a bear. Murphy is a *ick.