well I used the boulder creek defect detector it has 2 led's one each on its own pc strip all I did was take a file and made a notch in gargraves track so the led's would see the wheel sets as some engines and rolling stock smashed the led below the rail height needed to detect the wheelsets.
not having seen the lionel version not sure if this will work for you.
here is a web link to one I used https://www.bouldercreekengineering.com/
I did look at lionels looks like you would have to do major surgery to get it separated from the fast track I would seriously look at the one in link a much better and easier approach but up to you.
