What is the biggest tire size that u can put on a stock silverado without a lift? I want to fill the wheel wells up but not sure i wont to do a lift yet. Any opinions on this would be appreciated..Thanks

I've seen quite a few 285/70 R 17s. I think they look just right, which is what I'll be going with as soon as the bridgestones wear out. Probably going to go with 285/70R 17 BFG AT/KO

With that tire size u can keep the stock wheels to?

If I go new crew i will like to go this route.
https://www.tiresavings.com/tireShop.php?action=findCombined
type in 275x70x17 cooper

Yes you can keep the stock 17x7.5 rims. You may need to toy with the tire pressure to get the best ride, wear and handling but I doubt you'd need to even trim the air dam to make them fit.

285-60-18