the neck of my radiator broke last summer so i replaced it with a junk yard
one and we broke the nipple to the overflo by overtightening.... so i am very catious in this area.. i salvaged the radiator with a vacuum connector and so on my neck i have 2 hose clams instead of just one ...

so if you have the old radiator without the metal insert you might consider using 2 clamps and then just tighten them lightly until it does not leak...