k30 dually tire options. 285/75/16 vs 255/85/16 what size spacer

[dragn91]

Im in need of new tires for my k30 I'd like to run 255 85 16 tires if I can use then if I have to use a spacer I want to use a 285/75/16 both tires are around 33 inches but the 285 are obviously wider but they are also way cheaper and more plentiful. I found brand new off brands for around 140 a tire with a nice aggressive tread. My question is what size spacer will I need to run these. Or can i run the 255 85s without the spacer. I'm getting conflicting information. So if you have a k30 dually with 33 or bigger tires I'd really love some information