Diezel Herbert MK3 6l6 vs EL34



is it possible to BIAS the 6l6 Herbert MK3 to EL34 tubes ? Because i saw that there are 2 models (6l6 and EL34) for sale. If i want to change tubes for tone coloration on a 6l6 model it would be fine if its possible, but i dont know if there is a switch ar the BIAS range is big enough.
Thanks for the fast reply, 2 more questions:
1) Can i mix also the tubes, 2xel34 and 4x6l6?
2) Does the Herbert Mk3 has the Langer transformer like the Mk1?
Just pair them (or quad)
I used to run my MK1 with Wing C 6L6 in #1 and #6
Then EL34's in #'s 2,3,4,5,

Food for thought.
The MKIII I had sounded best (to me) with the KT77's