Some people put valves on the hoses and close it off. Check both lines from end to end. Another thing you may not be running a thermostat. Did you check that?
Don't understand the need for speed in the rain. Myself I wouldn't take a classic out in the rain....it's like thier worst enemy (rust) is encouraged. Been running BFG's and have no issues. I also have good 5 leaf springs and a 1" sway bar in the rear. I'm am adult so I drive according. I do...
I went with new springs but 1 more leaf than stock. It leveled out and had a really nice ride. Originally they sat a little lower in the rear. I hate shackles and don't like seeing them below the body.
Previously i replaced with a new hinge and it became a nightmare trying to adjust the door. Rebuilding your old ones sounds like good advice if parts are available.
I've always thought without a doubt the last full size years 71 - 73 were the most stylish American sport car. Finally a model that truely rivaled the corvette.
Just curious if you're replacing the door hinges. If you hang on to the old ones so you can see where to tweak and ground or hog nose as needed for alignment.