My Ford F 250 4x4 HD 1990 came with 33x12.50 R 16.5 LT Load Range D Tires but the tires recommended for this vehicle is LT 235/85 R 16 Load Range E. I need to tow 10,000 lbs. The two tires have similar max load requirements of about 3,000 lbs but will the Load D Tire be adequate for towing? I cannot find a Load E in a 16.5 size.

You'll probably pull better with the smaller OE tire size since it put the engine in the proper RPM range the taller tires raise your gear ratio that's for sure, But as far as the OE wheels it had 16"s so thats probably why you can't find the tires recommended