The middle two on each side have coach heads but a fine thread and are the right length to go through the cab floor and the wooden spacer and the frame, then have a washer and nut underneath.
The front ones are hex headed, and are longer to allow for a spring underneath. The shaft diameter is stepped so the spring cannot be crushed.
The rear ones are hex headed and extra long to allow for a spring.
Every bolt is quite specific and not a standard coach bolt. Ideally you need a serviceable used set or if Roy has them, buy them from him.
I bolted my 41 cab down so the bolts are not accessible to me now.
Here's a question: does anyone sell the correct springs for cab mounting?
Mart.