any hidden issues in switching from 20" to 17"?
 

I bought a used 07 LTZ ext cab back in May that had the 20" oem P58/5291 alum wheels and Goodyear LS-2 275/55R20 tires. With winter and hunting season rolling around, between the snow, dirt mountain roads, and wet muddy cornfields I know the shoes on it aren't going to cut it, so .... I'm thinking about possibly trading down to either a 17" or 18" wheel and LT all terrain type tires. I found a tire/wheel calculator that says either 265/70R17 or a 265/65R18 gives less than 1% speedometer difference. Aside from sizing the new setup properly to minimize the speedometer issue, is there anything else that needs to be addressed?

nope, people switch all the time. mostly upgrading to MT tires and bigger rims