that article has a list of tubes they use for both sockets.
i have not tried this tube, but it is highly regarded for the power tube socket on the ta-26(not specifically the 26, just in general). might give you a point of basis to search off of to see if the tube is right for you.
edit: your collection of 6sn7 tubes will work on the pre-amp(front tube). if you dont have one you like, it is the cheaper socket to roll with more options available as a lot of amps use that tube as a pre-amp(lots of hybrids and full otl’s)