Hi everybody!
Both Hammond xformer can't supply enough current for two 5U4 rectifiers. If you plan using the EL34s in your amp, the filament supply of the 373BX is too weak. If only hammond is an option take the 373BX despite its weaker filament supply: The sound is heavily influenced by anode voltages and this transformer is a better fit, but the maximum power delivered by the high-voltage winding ist a pretty tight fit.
Maybe take a look at the 177VA and 340VA TT toroidials.
Best regards,
Hannes