One of the first things I did after I got my Powermatic was to build an extension for the bed so I could push the tailstock out onto the extension to get it out of the way.  I made it 18.5” long, completely out of wood.  It is attached to the lathe by six bolts (3/8-16, 2” long) that fit into existing holes; no modification was made to the lathe.  

A piece of 3/4” cabinet grade plywood forms the foundation for the extension.  This piece is bolted to the tailstock end of the lathe.  A second, smaller piece is used as the end piece.  Everything else is cut from spruce from the lumber yard except two strips of oak that form the ways

                       

Build the Extension.

After cutting out the foundation piece, mark the locations of the holes for the bolts.  The easiest way to do this is to clamp the piece in position and mark the holes by reaching through from the inside. A wood clamp set at the bottom does a good job. The holes can be a bit oversize to allow for errors and also to provide a bit of adjustment so a good match is obtained at the top.  
Note that a 1/4” spacer is needed between the end of the lathe and the foundation piece.  The spacer is glued to the piece with a bit of medium CA.

Once a satisfactory fit is obtained for the foundation piece, mark the locations for the horizontal supports on the foundation and end pieces.  Use extra-long wood screws to attach the supports because the screws will be going into end grain.  I used #8 decking screws, 3” long.  It is a good idea to drill pilot holes for the screws to avoid any possibility that the screws may split the wood.  Do not overtighten these screws.

Cut the brace to fit and install it between the foundation piece and the end piece.  Any imperfection in the fit can be compensated by applying a fillet of epoxy around the ends of the brace.  In fact, you can apply epoxy at the ends of the horizontal supports as well if you have any concerns that the screws may not hold in the end grain.

To make a wider seat for the oak ways, install a strip on the top inside corner of the horizontal supports.  The strips should be 1/2 x 3/4” in cross section.

At this point, remove the tailstock from the lathe, turn it upside down, and look for burrs and sharp edges around the milled surface that contacts the ways.  Use a file to remove the burrs and ease the edge.  Put the tailstock back on the lathe.

The oak strips that form the ways are screwed to the horizontal supports.  Thin wooden shims can be placed under the strips as needed to bring them into good alignment with the ways of the lathe.  A coat of paste wax applied to the strips makes the tailstock easier to slide.  

With my setup, I did not achieve a perfect alignment.  The tailstock moves easily to and from the extension, but it makes a soft click as it does so.  This click used to bother me, but not any more.