[electroking]

There is a little tube substitution book by H. G. Cisin that sometimes
can be found on e..y. I used to have the 1965 edition, which
I misplaced, but I now have an earlier edition (missing its cover, but
I believe it is from 1959).

This book provides an extensive table of CRT substitutes. Tubes are
sorted by group, having the same deflection angle and pinout (and
screen size of course). The author gives advice regarding certain
changes, in particular he says that if a magnetic focus coil is to be
discarded, it should be left in the circuit and mounted as far as
possible from the new CRT.

Hope this may be helpful. Good luck.

P.S.: I will get my copy by Sunday and post the relevant table if
you are interested.