I have all Fastrack except MTH Realtrax O-31 curves inside a couple of Fastrack O-36 curves, I use the Realtrax Adaptor Track Piece to match up the the Fastrack Transition Track Piece, both pieces have one end to match up to their own track and the other end is a straight end cut that matches up to any O Gauge 3 rail track,. you can use the Fastrack Transition Track piece to match up with Gargraves or any other brand track, Tubular, Ross, Atlas, etc. or cut Fastrack straight across and insert pins. You may have to shim track for difference in height of both tracks. I have not tried matching these up but I'm sure there are many here on the forum who have done this and may give tips on doing this.