I tried to work out replacement slides with some HDPE washers. It was never quite right. Then I got my Sawsmith 2000 with the sliding carriage. A sliding table would be a better solution, I'm thinking of a single sided sled similar to the Shopsmith version so I don't wear out the sliding carriage. I did use it to cut 2X12s for stair treads, very convenient since I don't have a huge miter saw for cross cuts, but it's rare I'd cross cut wide stock like that.
The router mount was a great feature of the BT. I think did more routing than sawing on mine.
BTW: Here's the box that a Sawsmith table I bought from eBay came in to show that Shopsmith did plan on a router table for the Sawsmith, at least as far as printing a label. Someone out there may have purchase one. I saw in the list of prizes at the 75th anniversary included some refurbished Sawsmith tables. Not all that long ago they had a part number for the standard tables and I asked someone there to check to see if there were more but they said there weren't. None for sale I guess, but there were some in the back. I have all the tables that will fit on my rails now, but I'd replace one if a router table was available.
