should I change gears or tranny???

With those huge tires I would keep the gears and go for a trans with OD.

I installed 4.56 gears over the 3.55 gears that was in my 03 Dodge Ram with 22" wheels. I of course have a OD transmission. This was a big thing on the Dodge Truck forum I used to frequent. I believe Dodge got the word their trucks come with 4.56.... what I've been told anyways.

You might want to check this site out.... http://www.fortrucksonly.com/

I and some of the members been hanging out over there.