You probably can with some modification but you will risk loosing literal track control (such as the forward, neutral and reverse system or a combination thereof) in doing so.
Gargraves tracks come in 3 feet lenghts and can be used with Lionel Trains. But you have to mate the pins to permit the interchanging with regular 0 and 0-27 gauge tracks
Gargraves track works very nicely with Lionel trains and Gargraves makes special mounting pins to mate their track to whichever variety of Lionel track you have. There's also a growing collection of useful information on the Gargraves website (gargraves. com)
Very few Lionel train models will run smoothly on GarGraves (or any other track except Lionel). If you are setting up a display, you can situate the trains for show. But, if you are expecting uninterrupted movement, consider a more compatible track.
You are asking 2 different questions. Gargraves can be used with certain Lionel trains, it depends on what gauge they are. But you would have to make sure you purchased the exact same style and gauge of track for your lionel track to work with the Gargraves track.