47-55.1 Custom bench seat foam

[PDW HOTRODS]

I found an old thread with a pic of someones bench seat where they used the seat frame and took out all the springs and used plywood in place of springs. I have a 53 and I have the seat frame but both seat cushions are gone. I was thinking of how to make cushions. Doe anyone know what foam to use? The stock seat had wire to hold the shape, foam would need to be stiff to hold the shame.