Another episode of " Name This Part "
Top plates are 4 bolt Hooker header flanges to weld the tubes onto when making headers. You need the adapters for Hooker headers to use them . Once the headers are made you cut them apart
The bottom plates are W2 Hedman header adapters plates that bolt on the head and then your headers bolt to them.
I would be interested in them if the price is right to make patterns out of stainless