I bought a vintage Carvin X100B thinking I could swap out the tubes in the power circuit with ease using the handy switch built into them. As it turns out, he vintage model did not have this option! Can I have the amp re-biased so that 6L6GC's will work, or am I stuck with EL34's?

P.S. Strangely enough, the back of the amp has stickers that read EL34 under those tubes. If you remove the sticker, it says 6L6GC which seems like a good sign to me. your thoughts?
Out here you've gotta know where your towel is!