Alan, you will need to create a D1-3 mount to fit your chuck, which is on the big side for a Bantam, so you will need the locking pins as well as drilling the holes, do you have these?
Have you considered buying a D1-3 back plate available from "our" suppliers and fitting the chuck to that?
A lot would depend on the configuration of the holes and the register in the back of your chuck, and the size of the commercially available plates.
Chris Gunn