Hy lastchancetowing, you will also need to install a pilot bushing in the end of the crankshaft to support the front of the transmission input shaft. Clutches for the the trucks came in a couple of different diameters depending on the size of the truck, you can either look for a flywheel that is drilled to accept the clutch from the 261 or purchase a new clutch which will fit the flywheel you end up purchasing, hope that helps.
