I've got Alcoa wheels on my '97. I've been very happy with them. I got them through a distributer back in '98 at a real good price. The price now is almost double that, so I haven't wanted to spend the $$ to put them on my '96.
You probably don't want to run aluminum wheels on the inside rear. If you really want to do that, you will need to put longer lug bolts in the hub to compensate for the wheel being thicker in the center where it fits on the hub.
After you get done changing things, make sure you still have enough space between the dual tires. If they are too close, you'll either have sidewall rubbing or the chance of rocks getting caught between the tires - both lead to quick failures.