37" is tight on these trucks with 6" lift. 35" is tight with 4". I had 37/12.50-16.5s on 8.25" wheels I was planning to run on my '72 K2500 with 6" lift. I think that would have worked but rubbed a little. I sold that stuff and got a 4" lift to mount 35/12.50s on 9.75" wheels. The tires ended up being too old so I went with 285/75-16s, smaller than what you want. The 35s would rub with the wider wheels. I think 8" would be fine
35/12.50-16s on 10" wheels with 6" lift
35/12.50-16.5s on 9.75" wheels with 4" lift
37/13-15s on 8" wheels with 7" lift. Never rubbed