I got a 4.11 assembly for my '62 one ton. I found it in a 1968 GMC 3/4 ton suburban with a smallblock and auto. trans. Pull both axle shafts,the nuts off the front of the carrier and drop the driveline and the carrier assembly will come right out. Be ready-it's damned heavy. Reverse the operation for installation. I cleaned the housing out and washed the mating surfaces with brake cleaner and put a decent skin of hi-temp copper gasket silicone on the face of the housing just before putting the carrier in. I ended up using a small floor jack chained tightly to the carrier to lift it into place. Pick the best two axle shafts and do the same clean up and glue trick on them. Be careful not to over-do it on the glue,it'll screw things up if much of it gets into the bearings.
A 4.10 or 4.11 ratio should give you about 3,500 rpm at 70 mph or about 3,200 at 60 mph,as near as I can remember. Didn't seem to affect my mileage a bit,but it sure felt better on the highway. I suspect with the taller gearing my engine wasn't revving as high,but it was pulling a little harder,and thus was getting quite a bit less vacuum,so having to drive with a little more throttle offset the lower rpms.
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