I rebuilt my own ST-35 five years ago, and have thus far retained the stock circuitry (albeit with new capacitors on the driver boards). I may install EFB mods at some point, or at least put in a C-354 choke, but have yet to feel the need to do so. I agree with what others have said about using Sovtek EL84Ms, though I did find a quad of close-matching Mullard-made EL84s recently. Here's a picture of my ST-35, complete with old Dymo labels from when it was apparently part of KLH's research & development department, as it came from the estate of Daniel von Recklinghausen (who also worked for H.H. Scott, among other companies):
I probably am going the EFB route, but seriously, the choke is a wonderful option. That was my plan when I first got here. I don't know, maybe put it off board and do both?