These are sintered iron clutch discs for drag racing applications. These are not the finished product. The center hub has not been installed in these "blank" discs. These are most likely made by RAM Automotive. Ram makes these in all sorts of sizes and splines for all kinds of applications but the design is always the same. They come in different diameters as well. I've seen them as small as 8" for four cylinder engines and up to 11" for big domestics V8's like yours. The one in the URL is sold by Summit Racing, it's a 10 1/2" version and it's just an example of what RAM makes.

These are sintered iron clutch discs for drag racing applications. These are not the finished product. The center hub has not been installed in these "blank" discs. These are most likely made by RAM Automotive. Ram makes these in all sorts of sizes and splines for all kinds of applications but the design is always the same. They come in different diameters as well. I've seen them as small as 8" for four cylinder engines and up to 11" for big domestics V8's like yours. The one in the URL is sold by Summit Racing, it's a 10 1/2" version and it's just an example of what RAM makes.

References:

https://www.ebay.com/itm/RAM-5135-Sintered-Iron-Drag-Racing-Clutch-Disc-1388/...