It cruises fine on the highway but I would like my cruise RPM in OD to be a little higher then it is now. I think cruise at 65 is 2100rpm for me and my motor is barely at the bottom of its torque curve. If I had 4.88's my RPM would go up to 2300rpm and I would be in alot better cruise RPM for my truck.
I have a few more ponies (mild TPI 350) then a stock motor does in my truck but 2100 is just a little to low for my truck. With the added weight of a burb I think it would be worse. I know that is pratially a cam issue as well but this is a GM crate motor so I imagine a stock cam is fairly similar in grind. I don't know what motor you have but if it is stock get a little more gear to help make up for the lack of motor torque.
I used to run my 4.56's with 32" tires (31" actual height, my 35's are 33.5") after I did the axle swap, gears, and lockers. When I had that setup my truck ran like a raped ape and did alot better at cruising in OD. It kicked down alot less on hills because the motor was in its power band more. I even had a carb when I had the 32's and it still ran damn good with the 4.56's.
Now with the 35's and even with the TPI fuel injection I still don't have what I had, and I miss it. 4.88's would have put me back closer to that area I really liked.
Don't get me wrong I like my 4.56's but with the weight of a burb I would honestly consider the deeper gear. Run the numbers and figure out what speed you cruise at and what your motor likes then get the gears that match it the best. I cruise at 65-75 mostly so 4.88's match my setup best. If you cruise higher alot then a little less gear may not hurt, but always error on the side of the lower gear though. The OD tranny will like you more for it. The extra RPM helps pump more fluid to keep them cooler.
Harley