If a modern 6SN7GT like the Chinese Shuguang, yes, you can as even though they are marked as GTs, they are spec'ed more like GTBs and we've been using them that way for over 20 years with no worries. Don't do that with any of the boutique Chinese tubes like the Psvane- they are actual GTs.
6SN7GTB replacement
Hello, friends, I have a canary audio M 600 fitted with the 6SN7GTB reissue TungSol can I replace them with just the 6SN7 GT