I have a 1953 GMC, 5 window 1/2 ton pickup that I am slowly working away at. I have removed the box and began body work on it. I have also removed the torque tube and rear end out of the truck for tear down and rebuild. One I opened the rear cover I was greeted with rusty slime and water. Any thing in the slime was ok but anything above is got some rust on it. All this from a broken vent cap. Also the 17T axle splines are almost worn right out.

So when is pitting on the gears bad enough to cause fatal damage to the differential?
I have spent countless hours searching this forum with little answers to my next questions. What is the easiest way to save this rear end, either with a different 3rd member, another 53 torque tube rear end (hard to find a good one in canada), or a complete axle swap?

I would like to keep the truck as original as possible but i am open to modifications if original parts aren't available.

1953 GMC 9300, Five window 1/2ton