648 - I didn't spelled it backwards by the way.
EDIT: Don't mind me, I don't know how to count apparently. (My genius intellect thought 647 is succeeded by 646 for some reason)
Wario being an electrician feels like a natural fit to Mario's similar-yet-different plumber. Of course, most of the electric work we've seen him do is... done to him, through lightning strikes and electrocution, but not many electricians have...
I never really considered what it'd be like with Wario working for others since he's always in it for himself and with him as CEO it's the opposite and people work for him, but I agree that some sort of tradesman would be a good match with Mario...
I'd love them to do something like the old Wario Land commercials where you think it's a trailer for a Mario game and BAM! Wario jumpscare! It'd be such a cool homage.