Don't do any kind of welding on the axle until you get the sleeves installed. I've seen where heat from welding in C gussets caused enough warping that it made it very hard to get the sleeves in. You also need to do a good job of cleaning the inside of the axle tubes. The smoother and cleaner the axle tubes, the easier it is to get the sleeves in. Seen guys use a paint roller on the end of a drill to polish up the tubes to where they look as shiny as a clean gun barrel. Put the sleeves in the freezer over night to get them to contract some. Test fit the sleeves and see if they will slide in. If not, put some lube on them and plan on pounding them in with a bearing race installation tool. Once installed, you can put a couple plug welds in the axle tube, or run a weld bead around the end of the sleeve to keep them in place - your choice.
Ah, how beautifully the orchestra sounds before a rain! In a dry sunny day there is no way for the instruments to sound this way!