Back in the 1960s, when the factories wanted to go fast and the sanctioning bodies gave them room to do so, aluminum sheet stock was fed into the stamping plant body panel dies in very limited amounts to replicate the steel part it was replacing.
Due to the differences in material thickness and stress, this was a time-consuming process that likely resulted in a lot of waste as parts rippled and tore from the stamping job. After the set number of pieces were finished, the factory got them onto the specific vehicles they were intended for and that was it, making them rare and expensive today. Moreover, the thin material meant they really had no street purpose.
When AMD (Auto Metal Direct) began re-creating dies for the first-generation Camaro, they engineered a set of dies made specifically for doing aluminum stampings of the most popular bolt-on replacement panels – the hood, deck lid, front quarter, valances, and bumpers.
Unlike the pieces of old, these would use heavy-gauge aluminum that could stand up to street use, with the bracing and sub-structural components for added strength. In addition to being an exciting addition to their parts line-up, the practical benefit is eliminating about 120 pounds off of the car if all the available parts are used.