You can't derive a load rating from the UTQG (Uniform Tire Quality Grading) figures: treadwear, traction and temperature. Load rating is a function of the tire size, tire pressure and the internal construction. Treadwear, traction and temperature are roughly related to the tread compound, tread width and tread pattern and the grip and wear they afford.
When you look at a 265-70R17 printed on the sidewall of a tire that has UTQG data imprinted on it and you can't find the "E" rating, then you need to look for a large set of numbers and letters just after the tire size, usually in the same typeface. I expect you'll find 113T, or something close. The 113 part relates to the load rating. The "T" relates to on of several letters used to indicate speed rating. T, in this case, has no relation to the truck-style letter designation "E" for load rating in your example.
Is 113 equivalent to "E"? I don't think so, but I can't find the citation needed to be certain. "E" rated tires are designed for 3/4-ton (and up) pickups and SUVs, and are designed to around inflation pressures as high as 80 psi. If your SUV is a 3/4-ton Suburban or an Excursion, it might have come with "E" rated tires from the factory, but I'm not sure. If it did, stick with them. Not sure? Check your door jamb ID plate and your owner's manual.
If your SUV came with more-normal 113T load/speed rated tires, stick with those. They probably have an inflation pressure in the 32 to 35 psi range. Again, check the door jamb and manual to see what the truck is suposed to have. A previous owner might have installed the wrong-sized replacements. You can use a load rating higher number (114, 115), if you like, but you do not need to. Just don't go lower. This is sometimes a worry when people put low-profile tires on their rig - low profile tires often have a lower load rating.
Bottom line: don't mess around with load ratings. Always replace tires with the same load rating as the manufacturer recommended when the vehicle was new--especially with a truck or SUV.
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