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This looks to me like a vertical sweep problem, not a CRT one, although a loose and arcing connection almost anywhere could cause it.
The horizontal shift is probably from the collapsing vertical output tube changing the load on the flyback, assuming the vertical output tube uses B-boost from the damper tube.
It is hard to judge vertical linearity from this picture, however, with that said, it looks compressed at the top and stretched at the bottom.
Try substituting both vertical sweep tubes. If you don't have alternate vertical tubes, try tapping them gently and see if this changes the problem or you see internal sparking on the tube.
Visually inspect the vertical circuits for loose connections. If none are found try gently probing them with an insulated rod. Listen for the sound of arcing in the yoke assembly. You also can do this with an insulated tube for the rest of the set.
Note: The vertical output transformer may make a sound that matches this, if the plates are loose. To determine if this is a problem or not, tighten the screws slightly. If this reduces the sound, this is normal. If not, suspect an arcing transformer. (Smaller vertical output transformers don't have screws, just metal crimping.)
Have you replaced the grid coupling condenser between the vertical oscillator and the vertical output. If not, it could be breaking down.
A resistor (cathode, plate, grid bias) in the vertical output circuit could be breaking down. Check for changes in value.
If you are using the yoke that came with the Delco set, do a test with the one that came with the test tube. These are usually general purpose ones.
James
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