Won't fit. Different tube sockets.
Besides, bias are not set for 6L6s and 6V6s.
In any tube amp, don't even try to mix power tubes unless your amp has this switch or you are a skilled technician and know how to set the bias for those particular tubes.
Cause you'll end up taking your amp to the shop. The technician would probably say to you: "Why did you do something so stupid?"
Sorry about being harsh, but things could be avoided with common sense. Unqualified experimenting is not one of them.
