It's not even important to save the threads for the old valve if you're using r-134a. Just drill it out yourself and put on a decent adapter fitting that already has its own valve. How long did it take you to get that line out? I've got to do the exact same job on mine.

 

Good idea jhowell. I will attempt to find an adapter with its own core/valve. It took me about 3 hours. Some of the time was spent surveying to see the best avenues out and what should be removed or disconnected. You will need to do a lot of turning and some, not much, bending of the line, especially if that line will be reused. Did not require much disconnecting. In fact, after it was out, realized it actually required less disconnecting than was done. Walked away and came back later to finish. Things were clearer after a break. Good luck.

 

Mission accomplished! Thanks to all who contributed!