That's what I use, get pure lye from any hardware store. It's usually sold as a drain cleaner, make sure it says 100% lye on the bottle and it should be white crystals that you just mix with distilled water.
Maybe one of the more experienced guys in here can clarify, but I don't think this is the best idea (unless you plan on powdercoating or annodizing the part right after) for a few reasons. First, I've heard of nasty stuff happening to unprotected aluminum left out in the elements. Second, I'm pretty sure unanodized aluminum wont stay polished for very long, especially if it's on the front of a truck. Last, I'm not sure if this is a huge deal or not but it doesn't sound like you have a way of desmutting the aluminum after you strip it.
Don't take my word for gold though, I have a habit of being blatantly wrong
, I just wanted to make sure you knew there were risks involved.
On a paintball forum that a lot of us anodizers post on there are a lot of people who do something exactly like this and I've heard nothing but bad experiences from the people who do it, so be warned.