No atmosphere means very little thermal radiation is pulled from radiators.

I imagine the best bet would be to drill into the surface of the moon and sink your radiators into the ground, fill the gaps with a material that transfers heat well.

Easiest version of that would probably be to lay the radiators on or just below the surface and bury them in a regolith concrete mixture of some sort. Probably not as efficient as drilling straight in, but way less complicated I imagine.