Trans cooler lines 904

1965 Barracuda 273 with 904. One of the cooler lines have been compressed between the starter and steering, so I guess I have restricted coolant flow. Needless to say, I need to replace that line. I have measured the OD to be 5/16 on the tube. I guess ID will be approx 3/8? Can I use 3/8 copper tube to replace it?

I read that the flare nut is 1/8 NTP at both radiator and transmission. But from what I can tell there are flare adapters at all positions. Am I looking for a 3/8 flare nut for the new pipe?