Yes, with rebiasing. It would be good also to pull V1, assuming you use only the Vibrato channel, to take some of the load off the power transformer's filament winding. Ideally the output transformer would want to see a 4-Ohm load, but it will tolerate the mismatch. As a reversible alternative, you could replace the output transformer with a TO26 from Allen Amps. That will give the proper load match and with its larger core help you to take advantage of what the 6L6s bring.