Hi!

Good question, actually. *g*  I haven't seen the 
series, myself (I wasn't ever available when it 
was on TV.)  I've just been researching it on the 
web in order to ID some of my own cels. ^_^;;
From what I've found, the dub pages definitely 
refer to him as Tanaka.  The pages devoted to the 
original Japanese usually refer to him as 
Chuzaemon.  However, a couple of pages refer to 
him as if it's just his first & last name. ^_^;;  
Sorry I can't be any more helpful than that.  
I'll let you know if I find out anything 
definitive!

~Mala