In the market for a huge power increase? Then you're probably looking at getting a set of ported aluminum heads on your GM car or truck. Here's a sampling of what's available from the aftermarket community. Note that each head is just an example of what that company has to offer, so check their Web sites for a myriad of other heads available as well as possible options for the head listed (such as combustion chamber cc). Compression ratios quoted are for an otherwise-stock 5.7 LS1.