What's the best way to fix aluminum intake threaded hole for temp gauge sending unit?

I made a purchase of an Edelbrock LD340 intake before I went to Carlisle and saw I did pretty good on the price I paid compared to what they were asking at Carlisle. The one I bought was advertised as unmodified and it pretty much isn't. What is modified is the threaded hole for the temp sending unit. There is pretty much no threads let to grip and any force tightening the sender just spins. What is the best option to fix this once and once only . The intake is on the car and I would rather not take it off. I've thought about Heli coiling it or maybe putting a reducer fitting in 1/2 male to 3/8 female after drilling out to 1/2 inch and tapping the hole. Half assing it with thread tape and sealer did not seal it up.