The best thing is just get some old NOS GEC, real gold lions. 
Mind if I tap into your retirement to fund this purchase? Had I known..... I remember buying them for $38 a pop back in the 70's special order from Radio Shack of all places - but that was a lot of gig jack for a quad. I could have funded MY retirement had I bought a few hundred back then and put them on the shelf...

Much like all my investment choices.
Willabe, the only KT120's I ever tried was from Groove-ur-wallet Tubes back in the 90's. I didn't like them, nor the Chinese KT88 crap they sent me in exchange. Nor any other transaction I had with them - "It's not our tubes, its your amp." But you advertise specifically that they are for the Major. "Well they are not meant for those plate voltages." But you advertise specifically that they are for the Major. " Well........" You get the picture.
I do know a few guys who have used the newer KT120 in their Majors and they swear by them. It is womping good high voltage tube that can make a lot of power.
The thing that is bothering me with Psvane....are the packaging, gold plated base and pins, and tube coatings just a way to get another $40 more for a crappy tube? I mean look at the marketing shell game Sovtek is doing to grab a few more bucks out of the same tube (old name branding, etc.).
Jim