You should be able to simply replace the overflow tubes. They are simply pressed into the bowl, but may also have some sort of sealant. Aluminum expands slightly more than brass when heated, so after figuring out how you want to grab onto the bowl and tube, put them in the oven on max temp. Any hobby store should have suitable brass tube. If you can't get the exact size, you can sand a slightly too large diameter tube smaller by spinning it in a drill, or you could drill the bowl to fit the larger tube. Having a larger hole in the end than the factory part will not impact how the bike runs. Probably a good idea to seal the joint with a bit of epoxy before you install it. Put the epoxy on the outside of the tube so as not to risk plugging the passageway.
If your needle/seat assemblies leak, and don't have obvious visible damage, you can restore them by polishing the seat with some rubbing compound and a q-tip.
If your needle/seat assemblies leak, and don't have obvious visible damage, you can restore them by polishing the seat with some rubbing compound and a q-tip.