Abstract: A method of converting a sedan hardtop automobile body to a convertible includes severing the hardtop roof panel of the automobile body by forming cuts along the front of the continuous roof panel at the windshield and along the bottom of the rear roof pillars. A pair of structural reinforcement beams are positioned on the bottom of the vehicle connecting the vehicle's engine cradle and the rear transverse support which normally carries the two independent wheels suspension systems. A truss develop loads from the longitudinal beams to the surface of the wheel well lining and to the front shock towers. Transverse structural reinforcement is provided to the vehicle unibody at a position between the engine cradle and the rear transverse member and on the upper surface of the automobile floor pan. The transverse structural member fastens through the floor pan of the vehicle to the longitudinal reinforcements under the vehicle. The continuous roof panel is replaced with a fabric-like folding top.