Got to stay away from those solid objects...LOL!!! shouln't take to long to fix and pick up some RPM A-Arms if you don't already have them, they have a breakage waranty..
If you go with aluminum you would probley just end up breaking your bulkheads insted of your A-Arms. and IMO it is easier to replace a-arms, or just stay away from mail boxes, LOL!!!
Get some RPM arms and axle carriers. Aluminum arms will just put the pressure on parts that are more annoying to replace like the bulkheads/hinge pins and chassis.