First all CC tubes probably used the same envelope so physically
should work. CC tubes differed in dot size, screen tint & HV rating.
The KV rating is probably just the amount of lead in the glass.
Besides the HV actual gun voltages should be the same.
I would NEVER use a lower KV rating in a customers set.
If it were mine I might. Like I have said I spent 40 yrs surrounded
by sets & I dont have 3 legs & 2 feet !
73 Zeno
LFOD !