Yeah, it is different. I guess the the B has all 6l6, while the C+ has 6l6 mixed with el34.
I don't have a lot of experience with these amps. The only one I've messed with, the guy wanted me to tighten it up and make it less flubby. I don't remember what version it was, nor what I did to it. But he was happy with it afterwards.
I do however remember It had a giant Heat-sink on the back that served absolutely 0 purpose. Literally just riveted to the chassis, no heat generating components coupled to it at all. Oh and it did have 6l6/el34 combination.