As John says, converting a Bridgeport isn't really the best way to go. I'm also part way through doing one myself (I was doing it when I had the accident with the mouse on ebay) and their construction is nothing like a pukka machine. Having said that, there are quite a few BP-type CNC machines that were made as CNC from new, not just the Interact type. Get one of those with ballscrews, servos etc and fit a modern controller.