Following a two-day climb of more than 11 points in the share price of Lin Broadcasting Corp., Bear Stearns & Co analyst Kenneth Leon lowered his appraisal of the company’s stock Friday to “buy” from “strong buy.”News of American Telephone & Telegraph Co.’s proposed merger with McCaw Cellular Communications Inc. launched Lin’s price ascent. Lin is 53% owned by McCaw. The stock climbed 9 1/8 last Thursday, a 13.4% increase with 679,500 shares trading, compared with average daily NASDAQ volume of 85,800. After Leon’s announcement, the stock fell 1 1/8 to close at 75 1/4 Friday, with 328,100 shares trading. Although his move was prompted by the stock’s swift ascent, Leon stresses he still recommends the stock. He thinks AT&T, as part of its deal with McCaw, will ultimately assume Lin’s reins, a move he sees coming by 1995. Leon says the stock has a sturdy price “floor” and could in time be valued at 110 or higher.