I recently completed the ST35 on the "Tube Zone" base, using one of the 300VAC An-Tek toriods.
I had some minor "issues" getting the bias set to 35 mA, which turned out to be that the B+ voltage was around 345VDC, instead of the expected 365 to 370 VDC. These toriods have a "true" 115V rated primary, , so they will have less "300VAC" on the secondaries, than will the Hammond 272FX, which runs on the high voltage side.
I could get J/J tubes to 35 mA, but some NOS RCA's, and Russian 6P14Ps topped out around 32 mA, max.. I had to set the RK to about 350 ohms (the minimum was 345 ohms, with 510 ohm resistors) to get 35 mA out of the JJ/s, where 400 ohms is pretty much "normal" for these tubes with a more "normal" 365VDC B+.
I corrected it by lowering the "main" cathode resistors back down from 510 ohms to 470 ohms, and everything runs and sounds great! (I think this was the original Rev B and C board spec'e value).
I'd suggest using the 325 VAC version of this trannie, in order to get the correct B+voltage around 365-370VDC, at the OPT CTs.
Anyhoo, these An-Tek toroids do run at a lower temperature than do the PA774s and 272FXs, and they seem to have plenty pf power reserve, even at the somewhat lower B+ voltage, thanks to a fairly hefty current rating.
The slightly low B+ seems to have a different, and I'd say a "smoother" sound quality, perhaps the sacrifice of a couple of watts might be a good trade off... That's something which really needs instrumentation to analyze, rather than my less than perfect ears Yellow_Light_Colorz_PDT_06
FWIW, An-Tek has their own website, separate from e-bay, and the unit prices are a bit lower, as well.
www.toroid-transformer.com
/ed B in NH