Hi Harold;
I had the same issue. I had a machine shop make a 1/2 wide donut that I placed in the axle housing. The new rubber oil seals are thinner. Another stovebolter did the same thing and located a seal that fits the outer larger ring on the axle housing. This could let you use an even wider spacer. The only other fix I can think of is to hard chrome the axle and regrind it. I searched across the US and I could not find any place to buy or make new axles for this truck. There are photos in my photobucket of what I did.