A water pump can only pump coolant, not vapor. I suspect the coolant leaked out and the motor overheated. That the radiator bust is a consequence, not the underlying cause. A new radiator is needed. A new radiator costs $175 to $198 at
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the plastic expansion tank (where the coolant is filled) is $35. Given the prices you are hearing it may be worth trucking / trailering the car to another shop.
These straight sixes are known to blow head gaskets after about 150K miles due to the differing coefficients of expansion of their iron block vs. alloy cylinder head; yours may now be one of those.
There are two painful possibilities: A. head gasket replacement or; B. head gasket and piston ring replacement.
If the engine continues to overheat, especially if suddenly and quickly, then the head gasket is broken and must be replaced - no negotiation. Plus, if the motor burns oil then the rings have lost their spring temper (from being overheated) and need to be replaced. Note that one doesn't want to do the head gasket and then open the motor again to replace the rings.
These are ugly possibilities, hopefully that's all they are.
The only way to diagnose it further is to get it onto the road and see how it performs.
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