Anyone know a metallurgist they could ask about how welding on the axel tube affects its strength? I know any time you weld you create stresses. Should the tube be heat treated after to reduce stress?

 

I collect high-end knives and have read a lot on heat treating and metallurgic topics related to knives. I wouldn't even worry about this situation on a truck axle. Does Mopar heat treat the axle assembly after they are welded together?
If they don't, then just find a good welder that won't burn a hole in your stuff when he welds these on. To do proper hear treat, you have to know what the metal is exactly; what the desired RC hardness is; and how many heat cycles to run in a temperature controlled oven. And first of all, you have to bring the whole metal item up to a hardened state. Just find a guy that knows what he is doing.

 

It's recommended that you only weld 1-2" at a time on the gussets and then move to the the other side (using wet rags to cool welds). If you don't let the metal cool enough in between welds, it can melt the plastic in the stock ball joints and could warp the axle tubes.