DETROIT — A day after the Treasury Department provided a $5-billion lifeline to its cash-strapped GMAC financing arm, General Motors said it would reinstate cut-rate financing, including some zero-interest loans for up to 60 months, on many of its 2008 and 2009 models. The new incentive program runs through January 5.GM said a number of vehicles also are eligible for 'stackable' bonus cash of up to $4,250.The zero-interest rate applies only to certain 2008 models, including all Saabs, as well as the discontinued Chevrolet TrailBlazer and . The 2008 Chevrolet Corvette, Pontiac Solstice and Saturn Sky qualify for 4.9-percent financing; all 2008 Hummer models offer 2.9-percent rates, and all 2008 Cadillacs, 1.9 percent.Rates on 2009 models range from 3.9 percent on Cadillac CTS, and Pontiac G5 to 5.9 percent on Chevrolet Avalanche and Silverado HD.Inside Line says: The cash window is open again — but for how long? — Paul Lienert, Correspondent