Early Silverface amps would have been found with the last batches of the classic RCA tubes of the Blackface Era. Yet by 1970 the glory days of RCA were over, and we see Fender start to plug in Sylvania/Philips Preamp tubes, along with GE pre and power tubes. These tubes are typically branded “Fender” and sound less warm than earlier versions.
Thus, in our opinion the best vacuum tubes for Fender amps were made pre 1970, and because of this, we are left with the options already mentioned if you are chasing legendary tone.
If you are trying to return your Silverface amp back to 100% stock components you would have several options, as Fender was inconsistent with the tubes they used in this era.
Stock tubes for early Silverface (1967-70):
RCA/GE 12AX7A or 7025
RCA/GE 6L6GC
RCA/GE 6V6GTA
Stock tubes for post 1970 Silverface:
Sylvania/Philips (USA) Preamp Tubes (Sometimes Fender Branded)
GE 12AX7A (Fender Branded)
Power tubes: USA or even JAPANESE