Looks like you've already decided to proceed with the plan. For what it's worth, I've silver brazed brake bosses using MAP gas for both cantilever brakes and frame-mounted centerpulls on a few different bikes and I haven't had one fail yet. I'm always careful to get a very tight fitting miter. One bike with frame mounted centerpulls has been ridden nearly 20,000 miles since I brazed on the posts, and it's still holding together.
Go for it! I love to see forgotten old bikes being brought back to life.
Steve