A 34-foot floorplan with double slideouts and a 35-foot model with triple slides are available in Jayco Inc.’s new Seneca HD Class C motorhome, one of the new breed of brawny C-bodies. Built on a hefty Chevrolet Kodiak chassis, the Seneca is powered by a 300-hp 6.6-liter Duramax V8 turbodiesel engine.The coach features Class A-style baggage doors and an airy interior with North Ridge maple cabinetry and Corian countertops.