It's doable but it's going to take some time. You might have to do some milling to the extension to make it fit though. Make sure that you've got spaces you can put shims in and that you have a long sturdy flat surface to mount the lathe and the extension to. After you get everything half tight you'll have to figure out a way of running a dial indicator over the joint to the extension and adjust from there. If the bedways arn't flame hardened you could have some fudge work with block sanding. Having a straight good bed on a lathe is a nice thing to have. One of the Lathes at my work has about .003 taper in 3 inches right near the head stock, belive me you don't want that. Just my two cents.
Carl |