I have a Mark III purple stripe 60 Watt, running 2 EL34 (STR 447) green code.
Mike Bendinelli added the R2 Master Volume pot, biased it for EL34 and told me I could also run 2 6L6 red code if I wanted.
I put an Altec 8B in the combo. Combo has an X61 export transformer.
Sounds VERY nice. Very "orangey".