The 8 Ohm-only secondary might be a problem: tough to match the impedance of most speakers which can go down to 2 or 3 ohms for a lot of frequencies. But the higher primary impedance does have benefits: lower overall THD and the ability to handle wider speaker impedance swings. But, there's a reason why the transformer primary impedance is matched with the triode plate resistance: for maximum power transfer to the xfmr and the speakers. For SET's, with their meager power to begin with, preserving that power is usually the primary concern.
The most you want the xfmr Zp to go above the plate resistance is a factor of two, so you can get away with using it on the 245. The result will be less volume at a given pot setting.
For the 2A3 and 300B, not recommended. The power transfer is reduced too much to effectively operate. They're 3.5 and 8 watts, respectively, and any decrease in power will affect your system's performance.
The most you want the xfmr Zp to go above the plate resistance is a factor of two, so you can get away with using it on the 245. The result will be less volume at a given pot setting.
For the 2A3 and 300B, not recommended. The power transfer is reduced too much to effectively operate. They're 3.5 and 8 watts, respectively, and any decrease in power will affect your system's performance.