Hello and welcome!
I'll try to answer your question...
You can use an existing schematic for the 4x6L6 ODS with the following changes:
1) Output Transformer should reflect approximately 4000 ohm primary impedance (compared to the 2000 ohms or so seen in the Fender TwinReverb OT used in most ODS)
2) Bias circuit may need to have 1 resistor changed so that it can provide the correct bias range.
3) The B+ voltage should be limited to 400 volts or so (ZENER diode method or UR12s VVR circuit)
Have you considered building one with 2x6L6? (about the same power)
The only change would then be the output transformer (again, around 4000 ohm primary would be fine)
2x6L6 will be cheaper to re-tube as well.
Hope this helps.
Tom
I was thinking along the lines of using f.eks. a 12au7 for output stages, or some low power pentodes. I think I saw someone using a couple of 6au6'es somewhere (not i relation to a Dumble or Wreck clone)
You don't need to make a DUmble with low output power section, since a Dumble will wound great at volume "1" IMHO.
Check pictures of Robben Fords or Larry Carlton's rigs to see that they don't use the master above "5" to get their tones out of a dumble.
However, you could just build a little Fender champ output stage to be feed from pre-out of a Dumble clone. If you want to ad output tube (overdrive) coloration. Just an idea