I received one of these and I'm going to use it to try and resuscitate an MS-2931. With the sizing issue, the HV might simply be a bit too low (lower HV produces a larger image due to reduced electron travel speed). With an HV probe, the HV can be tested.
I have the same situation. Did you find the pinouts? I'm not sure on spacing but this might be known as a 10 pin dupont connector. Should be relatively simple to make cables for with the pinout. Without I worry about the shift modes.