Speed related vibrations, particularly in the 50-60 range are usually tire balance issues. You said you had them balanced and rotated. One of those actions is you problem. I've been there myself and the Wangler is very susceptible to vibration from tires that are not PERFECTLY balanced. Swap front/rear on each side at a time to determine the tire(s) that may be the problem.
2003 TJ, 33" BFG AT, 2" BL, 2" BDS spring lift, Truck Lite headlights, Homemade sunrider top.