Sorry Guys, I feel like I am hogging the forum here.
Further checking tells me that,the data/specs, barring the Htr. Specs at 2.5 Volts for the 2X3 and 5Volts for the 5Y3, both of those two tubes are alike. They both draw 2 Amps. and safe operating voltages (higher than I first thought) are also identical. However, as I said on my first post above, 350 volts, Plate(s) to Centre-Tap on Transformer would be about the normal operating voltage on your set. Which at the input to your filter choke/field coil, would be around 250-270 volts DC. So use the Data supplied at Frank’s Site, or any manual for that matter, for the 5Y3 as your reference. and you will be in save water.