I'm not bending the aluminum, actually. The 90 degree bends are joined by rivets to a common piece of angled aluminum stock.
OK, I lied a bit. I will do some sheet metal bending for the ducting from the radiator, but that should be it. For bending it, I will be using 2x4's bolted together with pieces of shim material to make room for the sheet metal to be inserted (saw that in a home repair magazine).
I don't have a sheet metal brake, unfortunately. Actually, I could probably use the one at work, but I'm stuck at home (except for brief forays to the store and for meetings at work) until my wife is done recovering from delivery (another 1-3 weeks for delivery and another 2-3 weeks for recovery).
Redneck motto: You do with what you have.