heli-coil

Have them try this first, have them use a bottoming tap and go right to the bottom of the hole with thread. If you end up with 6 or more good threads have them install a length of all thread (grade 8 threaded rod) and give them the rad hose neck. Have them cut the length figureing in neck flange width, gasket, nut, flat washer, lockwasher and 2 threads showing above the nut when tight. This shouldn't take them more than 15 minutes. All most forgot, use high strength Lok Tite on the stud threads that go into the manifold. If you have them install an insert (much prefered over Helicoil) you're looking at atleast 1 hour shop rate for setup, drilling, cleaning and installation.

Terry