Made some major updates to the article. Also changed the links above since the URL has since changed.
Added some more disclaimers and clarified how much weight they can support. Each block could support a full size SUV, times 4 blocks they are sufficiently overbuilt for my needs. Of course, make sure to customize them to the vehicle that they will be used on and to your usage. Also added this pic to the mechanics' tips. Learn from other's mistakes. Not my pic but I wanted others to see it. That oil pan could be your head. Complacency = injury.