An adapter kit for use in connecting an engine to a transmission is disclosed. In particular, the kit is useful in connecting a Harley-Davidson motorcycle engine to a Volkswagen automobile transmission. In general, the kit comprises a bell or second housing, a flywheel, and adapter elements securing the flywheel to an output shaft of the engine, along with assorted other assembly components. The bell housing is interposed between the output shaft side of the engine and the housing of the transmission. The adapter elements for securing the flywheel preferably comprise a flywheel adapter and gland nut which secure the flywheel in the proper position to the output shaft of the engine.