If you feel adventurous, there's a low-temp brazing rod for aluminum. It melts at 700 deg F so you can use a common propane torch for the heating. The stuff adheres well to clean metal, and is stronger than the base metal. You may be able to clean the original holes, fill them with the brazing material, and then drill and retap the holes. I've used the stuff to make lap joints in aluminum bar stock with good results. Just make sure the metal is clean (degrease it and scuff it up a bit - it doesn't have to be too shiny), don't over heat the metal by keeping the flame moving and only heat until the brazing rod melts (heat the base metal not the rod). The rod will melt when the base metal reaches the correct temp.
You might be able to find the stuff at HomeDepot. If not, use the following link:
Hobart 770206 - 8 Pack Aluminum Rods - 18-1/2" Long - Toolfetch.com
Don't know if this will work, but it may be worth a try if nothing else works.