For my first tours including a TA and other long tours, I used a Blackburn EX-1 rear and Nashbar or Performance low rider clone. That was fairly heavily loaded and they worked out fine. Since I have been packing lighter and using a road bike I switched to Axiom racks and really like them. They are actually much sturdier than I need for my light packing style and would be fine with a heavy load. Tubus racks are nice but the price hit is a bit much when much cheaper racks are quite adequate.

Just food for thought, but 50-60 pounds is a heck of a lot of gear. I find more like 1/4 of that is plenty to camp and cook in comfort even with some extras like my fly rod. It is much more pleasant to ride a very lightly loaded bike and to have a reduced pile of gear to dig through for stuff. If you have any inclination in that direction I highly recommend giving lighter touring a try.