I have a 3.08 rear in my '55 1st GMC Suburban. Engine is the GMC 270 and transmission is the ever popular SM420.
I find it very drivable as long as it is empty. Hook a trailer on behind it and it does not have enough grunt to feel happy going down the road.
If you want a good highway friendly driver, and do not expect to haul much of a load, I think the 3.08 is a pretty good choice.
If you want to pull a heavy trailer you have the wrong motor to start with...