You can use a keyway replacement from Tube Depot,
https://www.tubedepot.com/products/octal-tube-keyway-replacement
The filament pins of 6sn7 are 7 and 8, you can use a DMM ( digital multimeter ) to identify the filament pins by using ohm meter, other pins will show open circuit except pin 7 and pin 8 have resistance reading.
https://i.pinimg.com/originals/d7/c6/e4/d7c6e4adc921afe65ab6af7ebeec279e.png
https://www.tubedepot.com/products/octal-tube-keyway-replacement
The filament pins of 6sn7 are 7 and 8, you can use a DMM ( digital multimeter ) to identify the filament pins by using ohm meter, other pins will show open circuit except pin 7 and pin 8 have resistance reading.
https://i.pinimg.com/originals/d7/c6/e4/d7c6e4adc921afe65ab6af7ebeec279e.png