Which city billionaire will get his chubby white hands on the General Motors building? The Observer the other day suggested Daily News owner Mort Zuckerman was in the running to acquire the iconic midtown building, but his people told the Sun today that it wasn't so. (Could he be feeling so diminished by Rupert that he spread the rumor to make himself look cool? Just asking!) Quoting "sources with knowledge of the proposals," the Sun says ground-zero developer Larry Silverstein has made an offer, possibly in partnership with the California State Teachers' Retirement System, of more than $3 billion. That would not only be a record-breaking price for a building in Manhattan, but it would go a long way toward easing current GM-building owner Harry Macklowe's credit woes — he currently owes various lenders around $7 billion. And you thought your credit-card bills were high.