The 14 bolt is a good solid rear end but hangs a little low in the middle. I think they quit using the SM420 around 1967, so you probably have the SM465 which is plenty stout. As for the front axle in the Suburban, is it disk or drum brakes??? I don't know much about the Rockwell T-case but you can get a NP205 with the factory adapter from a salvage yard and have a good set up!!! You will have to outboard your front springs unless you plan on cutting the axles down or converting to coil. Coils are my plans if I ever get caught up on everything,