Tire size

[AuroraGirl]

If the door tags are missing the RPO codes on glove door identify what factory originally installed.
With a tire sizing application or chart. You can mix and match, profile ( aspect) with width to get the diameter and footprint you want.
The 245 looks to narrow for my K2500.
I have 275/ 70 / 16. Tire width looks correct. Speedometer is 1.5 slower than actual GPS ground speed. I can live with that. Good luck.

fun fact, in some year at least 95 GM started allowing a tech 1 or tech 2 to change the wheel size on at least GMC vans, I would assume trucks too. if you find a friend with a tech 2 you can correct your size. I corrected my uncles 95 GMC vandura to the size he had coincidentally put on and it fixed his speedometer reading