Frankly, I would expect that if the bleeders were rusted in place that completely, the bores of the cylinders would have rust in them, too. If it were me, I'd get new ones. Come to think of it, I just did. The master cylinder and all the wheels cylinders on my '51 GMC (last licensed in 1976) were rusty to varying degrees. Two of the wheel cylinders might have been salvageable. Didn't do it - I replaced with new all around. That's your life you're talking about - brake failures don't always give second chances.
David Bush
