Rims

I was wondering what size offset should i get for my 98 bagged f-150 i found a set that i like that are 20x8.5 with a +9mm offset and i was wondering is these would work if not could somebody please give me the correct offset so the rims will tuck without hitting the fenders or bedside!!!

DOES ANYBODY KNOW!!! I need help quick!!!

i know a 9 isnt going to work i think fords need like a 25 or 35 not real sure but i know a 9 wont work