The Cummins part number for the flex plate only is 3918957. The cheapest new one I've seen for sale was $325 on ebay. Here's that listing. Cummins 3918957 for sale online | eBay Just be aware that is only part of the kit to install the GM automatic to the Cummins. There is a crankshaft adapter part 3907701 and the wave ring assembly 3908124 plus some bolts. All the parts also exist as a complete kit under part FW9043. Wouldn't be surprised if that one isn't over $1000.