Lundahl LL1664s if I'm not mistaken. Glenn thinks I'm crazy spending so much money on high dollar parts, but these are actually very reasonably priced compared to the crazy Tango and Tamura transformers from Japan. I think Lundahl hits a good sweet spot in terms of price/performance, though that is not really based on anything but my own gut feeling. They're actually not much higher than One Electron which is considered a budget transformer, but the price of the metal covers has to be taken into account too so overall they are a little expensive. Lundahls are really ugly looking without the covers so they're pretty necessary.
I would like to get some custom O'netics transformers from Bud Purvine for my future 300B monoblocks, but maybe it would be easier to just do Lundahl again. Glenn seemed to really like the Lundahl main power transformers too.