Ah, right. I had yet to move on to that step. I wasn’t thinking I would use the AS-1T300 PT for the RR763V, but was wondering if this one would work: https://www.antekinc.com/as-05tc300-50va-300vx2-transformer/You don't need to increase the filtering, but you can if you want to since the transformer is slightly oversized for the load you're going to have.
The one thing you haven't mentioned is the bias supply. Since you won't have a center tap, and you'll be using a bridge rectifier, you can't just hang a reverse biased diode off the secondary. You're going to have to create a capacitor coupled bias supply.
My suspicion though is that it wouldn’t have enough DC current to handle a 12AX7 + 12AU7 + two 6V6 output tubes but I still need to figure out exactly how to calculate that. My best guess is that those tubes would consume around 100mA and it looks like that particular 50VA PT would only be around 84mA with the secondaries wired in parallel. I could be completely wrong.