If I recall correctly, I connected a Teensy 3.2 to a GPS using USB-Serial using no other hardware than a cable. It's possible I wired the GPS to hardware TX and RX pins of the Teensy, but I don't think so. I'd be...
Wow. Congrats on getting it working!
I'm sure I'm not the only one who is curious about what marvelous gadget will you put this in and what will it do?