You may want to get a radiator cap with a hose fitting on it and tighten up a hose clamp on the bottom hose so that when you turn on the water, the pressure in the radiator will let you know if the core is bad. This might save you a few dollars and let you know right away if the rad needs to be repaired or recored. If you've busted a hole into the top of the master cylinder, there are probably chips in the reservoir and I would be afraid to use it.
