I have a 5.3, my friend has same truck with the 4.8, and my 5.3 will out tow him hands down. Taking off with a full size truck on a trailer feel a lil sluggish, at about 55 to 65 you have to watch your speed, my 5.3 wants to run 70. I have 4.10s to but not a lot diff than the 3.73s I'm running 33in tires so it's close to when it was all stock. You already have a 4.8 I'd do gears, and bump up the stall so you can stay in the mid range power that will help a lot. Tune will also help