If you want to take your inner fenders out and put trailer fenders in there you will have to relocate the battery, overflow tank, and fuse box or make brackets for them to fit. I wouldn't think you would have to tub it for 20's. I had a 01 ext cab lowered 3 in the front with 24's and all i did was roll them up a little on the inside and it never hit in the front. I would lower your truck throw the rims on there then if it hits try to roll it up were it hits.