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There is no torque spec for radiator support bolts, as they are not intended to be drawn down tight. The idea is to allow the cradle to rock when the frame twists and not rip up the front end sheet metal. All you're looking to do is put a little preload against the springs and put a cotter pin in the hole.
There's an old thread on here where a couple people (including me, IIRC) measured how long the springs were when the nut was tightened. You don't want them so flexible that the front end is flopping around.
iirc, the bolt has a hole and uses a castle nut for a cotter pin. If the hardware used is original style, it should be just a matter of setting the nut where the cotter pin goes through, and you're good to go.