3 rail 031 tubular to snap tracks is a snap (pardon the pun). Just snip off the plastic tabs and substitute normal 031 metal pins.
I believe some of the K-line snap track came with adaptor pieces but I could be wrong.
I have two of the 031 switches and they work great with my Beeps, Plymouths, and starter level steam engines. I would love to get more!
Jim H