BROWNSVILLE (AP) — Two Florida men are free on $3,000 bond each, after being charged with conspiracy to murder their Brownsville business partner, William Riggs, 42. Flynn Clark, 49, of Miami, Fla., was charged here Tues day. Robert Gertz, 34, also of Miami, was arrested Feb. 15 as he stepped off an airplane ar riving from Tampa, Fla. Brownsville police chief Gus Krousse said the complaint stems from a business disagree ment among the men over a meat packing plant they oper ated jointly in Matamoros, Mex CO,