Cooling problem...

That is undoubtably the hot-water-to-the-swirl-tank, then to the radiator, which in stock form has a very thin flange to seal off pressure. If this is corect,be sure the flange is perfectly flat, then use non-hardening 'Permatex' on the gasket to the pipe flange & let it set up before bolting it down on the block. Many Pantera owners have takes all the stock mild steel water pipes off due to massive corrosion, and replaced them with stainless steel pieces. The flange is thicker on such pipes, making the seal more sure. All the major vendors sell such kits.

If you have the stock upper pipe and are in need of a replacement. I have an upper after market stainless non polished pipe that was installed on my car prior to me buying the car. It has been on the car 8 months. You can have it for $45 plus shipping.
I bought a comlete pipe kit that had an upper pipe in the kit.
Email me at kgovett@ev1.net
Thanks Kevin