The Red Sox have agreed in principle with the Rangers to a trade that will send Mike Lowell to Texas for catcher Max Ramirez, according to a baseball source. A money issue has also been resolved, the source said. Lowell will make $12 million this season, and the Red Sox will pay Texas some of his salary. The remaining hurdle is medical clearance, usually a formality in most deals, but given the history of Lowell's hip injury, the Rangers could conceivably back out.