I think this question has less to do with the length of your limbs, and more to do with your hip insertion points.
I too have long limbs (femurs as long as my torso) - but when it comes to foot placement (for me) hips are the main issue.
I try to keep my toes pointing fairly forward, with my heels spaced slightly outside of hip width, but of course everyone must find their ideal placement. If I wide stance powerlifting style squats, my hips are f**ked. I guess I have insertion points which dont favour squatting with a wide stance.
As for the knees, they should track out to the outside of your feet, this is the healthiest path which puts the least stress on the knee joint.
For me, being long limbed affects how I break at the hips. That's something I had to work on. Something like a timing issue.