Can anyone tell me if there is an external difference in a Dana Model 60, 70, or 80 rear axle other than the different carriers inside? Are the Maximum Gross Axle Weight limits the same, do they bolt on the same, etc? I have a model 80 rear diff and want to change ratios. I need to change carriers to do this and it has become cost prohibitive. Can I change to a Model 60 or 70 and just go to the junk yard and switch out the whole shebang? Thanks in advance for any help.