Dave, if i am not mistaken you are pretty much 3 rail. One tvs per engine. The tvs would be installed across your positive pick roller and the other end of the tvs to your engine ground which shares your outer 2 track rails. The tvs listed above is not polarity sensitive.
I prefer to pull the shell and install near the board. You may be able to turn your engine over and install at the trucks from the roller to truck ground. Hoping others will chime in with how to's.