Bead rolling

[SA Resto]

Hi All
Just joined. Want to build my own motorised bead roller. Have some ideas, but am always open to more.
Want to know what would be considered to be "standard" center to center distance for the shafts that the dies would mount to.
What are considered "standard" sizes for the ID of the dies?
What is the most common OD size for the dies?
Would appreciate some guidance.
Thanx.
Claude