Zenith HV regulation issue

[drh4683]

I'm currently working on a '71 Zenith color set that uses the 14B9C50 chassis. It had a HV regulation issue where I couldn't get the HV to adjust below 29KV. It turns out that the VDR (voltage dependent resistor, aka "varistor") in the regulation circuit was defective. The schematic calls for p/n 63-8161 which I had on hand as NOS. I subbed it in and noticed that the regulation was not adjustable even in the slightest, it was actually more adjustable with the old VDR in place. I figured maybe I just had an oddball defective NOS part. It seems possible... So I went ahead and did a search and discovered that Talon electronics had three NOS 63-8161's in stock. Since I work on these sets frequently, I bought all three. They just arrived today and was ready to put one in. These varistors were made by different manufacturers for Zenith, typically slight physical differences, but electronically the same of course. That was very typical. When I clipped in the three different NOS varistors, I noticed that I had a wide variety of results when subbing each of them. With the first one, I could get the HV down to 25KV but that was at the very bottom end of the HV adjustment range. That's no good... Then I tried the other two which were physically the same construction as my defective NOS one that I had from before. Interestingly, both of those failed to work as well, not even responding to HV adjustment, almost as though they were wide open. So I had an NOS Workman brand substitute, an FS1220. With that clipped in, I got a perfect HV range adjustable between 20-30KV like it should be, so I know for sure the trouble is indeed with these VDR's and not some other problem in the regulator circuit. Apparently these blue colored Zenith VDR's become defective with age regardless if they were in a circuit or not.
Since I have results all over the board, I would like to install a modern MOV (metal oxide varistor) in place of the original. I know NTE makes a bunch of different types that I can pick up locally at Fry's. The problem is, I'm unsure which would be the correct substitution. The Workman one worked, but who knows how reliable it would be in the long run. The NTE cross reference comes up with nothing when I put in the either the Zenith or Workman part numbers.
According to my 1983 Zenith parts manual, the original 63-8161 was replaced by p/n 863-1060. It appears that numerous other varistors were replaced by the 863-1060 as well, but unfortunately I have no technical data on this in which to find a good substitute. Maybe someone has other cross reference materials and can help me out, or has even run into the varistor problem before and knows of the correct NTE part to use. It would be much appreciated!