T-300 gear ratio ???

I have a 2003 T 300 and it has a 3.90 rear end. It has 24" tires on the rear (22.5 on front) Book says it originally came with 22.5. I need the extra torque as I get off road sometimes and in hill country and rarely on the interstate. How much difference will it make if I go to a 22.5 Will it be noticeable?

 

I don't need more speed, I need more power. This once was a box truck used in the flatland of the mid west evidently. Some one put 295 R70 24 on it. When I drove it home I noticed that it dropped down speed quite fast on the hills. I checked the line sheet on it and it originally came with 22.5 295 70 on it. I am putting a septic pumper tank on it. My other tank truck has 4.10 rear end with 22.5 tires on it. If you get out on flat open road, yes it is geared a little too low. But most of my driving is on county roads. For some reason the T-300 seems geared too high as it has no power in high gear. I was just wondering if putting 22.5 tires and wheels on it would be worth the cost and if I would gain any noticeable difference. Plus it already has 22.5 on the front. I think it would be best of all tires matched all the way around. That way I wouldn't have to keep two spares on hand.