Instead 6GH8A will be possible ECF-82/6U8A

Hello Folks!

I receive a few "Ulton" branded ECF-82/6U8A drives, which I want to be 100% sure that CAN BE...?, used instead the "Original" fitted 6GH8A tube in my also Gifted Dynaco Stereo 70 Series 2 power?

Your expertise advice or opinion will be extremely helpful.

Thanks very much ann al the best listening to all of you!

I think the ECF82 is a direct replacement for the 6GH8A. A Sonic Frontiers dealer sold me a pair of Telefunken ECF82 to use in a Line 3 preamp in place of the 6GH8A. They worked fine and were a good improvement over the stock tubes.
7199 is also functionally the same tube but with a different pin out. You would have to rewire the socket to accept 7199. That said, 7199 should be quieter due to the no-noize twisted filament.
They are very similar but not identical and the amps will more than likely sound different - but should work with no problem (no guarantees here). The 6GH8A's were not the kit "originals", the 7199's were; but because they became scarce the sockets were rewired to accept the 6GH8A. These tubes are still available and are IMO the best driver tubes for the st-70.