Cummins Diesel Engine Flywheel Housing 3971630. Please research/ensure fitment of part to your specific vehicle before purchasing. Custard Core Supply provides the highest quality of new, new take off, used, and core parts. We provide a variety of gas and diesel parts to our customers. Based in Dallas, TX Custard Core Supply has been in business since 1998. If you do not see a product you are looking for on our page, please reach out!