My 95 GMC Vandura 2500 likes to tow in 3rd. The only time I have pulled a loaded trailer any distance in OD was coming home from Memphis last month with a mother of a tail wind. I have an open trailer.

My drivetrain is: 350 tbi motor, auto (and yes lots of people say don't tow in OD or it will shift too often, burn up, etc. I plan to add a larger cooler to the trans next off season), tow package and a 3.4x gear. I like the tall rear end because when I tow in 3 I don't turn a zillion rpm at reasonable speeds (60-70mph depending on conditions). Gets 8-10 towing, 12-15 empty.