[DaleHCook]

... make sure that Pin 1 of the 6A8, 6K7 and 6H6 was not used as an interconnect terminal and connect them to chassis ground.

And that is something which I forgot to mention. In chassis which were made with glass octal tubes pin 1 was sometimes used as a tie point. If you want to use a metal tube in such a socket, you will have to provide a new tie point to which you can move that connection, in order to ground pin 1.

The first octal tubes were introduced by RCA in 1935, and all of RCA's octals were initially metal tubes. Other tube manufacturers, such as Sylvania, started building octals in glass envelopes, such as the 6A8G and 6K7G, to avoid paying RCA to license their metal patents. The "G" designated the glass envelope. When RCA started making glass versions of metal tubes they used the designation "-G." I'm not sure when RCA introduced their glass versions of octal tubes, but it was before 1940, as they are in RC-14.