Hober Mallow wrote:
there's never any mention of George ever being named Sam Francisco
I believe there is a single reference to it, albeit an obscure one. In at least one episode, George has a "I Love San Fransisco" mug which has been altered to say Sam.
And yes, the spelling of Sikes's name was changed, probably for some sort of legal reason.
I asked Kenny Johnson about that once, and the real reason is simply that he spelled it like he heard it without consulting the movie and goofed.