The standard internal spindle taper for Dore Westbury is 2 Morse Taper, so any tooling for that will do, plus a drawbar of course to match the tooling. If the machine has been built to design spec. there will be a Myford size threaded nose on the spindle end which can be used to hold a collet chuck.
From the simple Morse Taper collets, size to suit your cutters, to more expensive ER collet holder and collets, again to suit your tooling, but ER have a tolerance on size. See John Kennedy's link for a suitable ER collet holder.
The usual recommendation is to start off simple, with plain 2MT collets, then upgrade if necessary. It depends what range of cutter sizes you are going to use.
Choice of collets is very much a personal choice, so there will probably be a wealth of conflicting recommendations!
Edited By Robbo on 25/11/2014 09:49:44