How can I replace a tilt up garage door, with near zero clearance, low overhead?
If the problem is only the track/hardware (and it looks like your door is in pretty good shape from the photos) and you could stand to wait for a little while, I have an alternate suggestion. Get friendly with a local door company, not a chain company, and see if they could come up with some used track or hardware (whatever is causing you problems) from a door they take out. Chances are they could come up with it within a month (I took a 7' one piece out today. I'd offer you parts, but I'm in Arkansas and I don't see you making the trip for it). It's a bit of a trick to put an opener on a tilt-up door but it can be done in most cases.

Torsion to the rear should be able to work if you do replace you current door. Tell them to bring the cables over the top of the drums so they are up higher.