Q: Predicta replacement CRT

[Electronic M]

Look at the datasheets for the 2 tubes. If the current draw is the same they will sub just fine in a series string. Back in ~1958 line voltage was assumed to always be 117V, but in 2019 line voltage is always assumed to be 125V...An 8 volt increase.

In an original series string with original CRT that should be divided evenly across the whole chain and not cause harm. The higher voltage CRT heater should absorb a good portion of that change and soften the amount the rest of the string has to absorb.