Hey, you'll be able to drive it with ANYTHING in it. Look at it this way: 4.88 isn't even 10% more than the 4.56 ratio. You can CERTAINLY run 10% more RPM's since getting "great" mileage (an oxymoron for most of our trucks...) won't be important with the kind of use you're citing.
So, for a "nearly" dedicated vehicle, go for the 4.88's! (changed my mind that quick -- but it was based on what you said...)
If you do the install, and the 9" has c-clip axles, make sure you pay attention to install instructions carefully. 4.88's have EXTREMELY thick ring gears and the center pin of the differential can have a problem clearing it. I had that with my 4.56 and didn't address it which meant taking the ring gear back off to address it. Don't be me!
Nevermind. NO WAY can a 9" have c-clips because of the way it's assembled. It would have to be a full floating axle, I would think.