What size tires and is the gear set the original ratio?
I don't currently have a working speedometer and I don't yet have the cajones to hop on the interstate but I've had no trouble keeping up with slower traffic on state highways in my 51 1/2T (216/3spd/4.11/16x7.75" sidewall) ... figure most slow drivers do +/-60 w/a 55mph limit. To be honest, I'm more concerned about stopping or maneuvering quick enough should something happen in front of me.
