If it has a Keying tube, some do, mine doesn't, It will take the 6AQ5A or 6HG5
You can use the following for Drivers:
6KV6A
6JT6A
6JG6A
For Finals you can use these:
6MJ6
6LQ6
6JE6C
6ME6
I put them in order of preference. It is not advisable to mix and match. Try to keep them all...