O.K., on your current rims you can go a little taller.
Be aware this will steal low end power and screw up your odometer reading and you may need a suspension lift.
HD T-bars and AAL's at the very least. You can re-gear and restore low end power.
If you just want to go wider you need to get 8" wide rims.
Now you get into backspaceing issues...

Are you doing this for looks or do you need the added width and height?

BTW, nice looking truck, I like that color!