[Christ]

Well, does it have plastic end tanks?

If Yes, unbend the tabs that hold it, apply a new bead of sealant all the way around it, then clamp them back on. If the radiator core itself has a hole in it, yes, you can solder/braze it with no problems.

If you have metal end tanks, and they're welded on, just solder up wherever you're losing pressure from on a standard pressure test (the adapters are easy to make for pressure testing radiators and intercoolers, etc.)