Screw an iron block at that price. Run what you have until it holds you up. In the meantime find a real deal on an LM4 aluminum block 5.3. If you're savvy you can convert a truck harness yourself to save a buck. We also passed an RCR to allow cheap aftermarket accessory mounts instead of the ripoff prices CL fiends are demanding. I found myself a $225 LM4 at the pull and pay some time back, hoping to find a spare without a hole in the block at some point. I've hunted down the LS1 rack, k member, steering shaft, plastic tank, etc but just know the swap process, at least on a 4th gen, is fairly involved. The early early LS1s had return lines, so hunting down those rails will be a necessity for that 3rd gen. Not an overwhelming asspain, just something to consider. It's more than a motor and mounts to get that thing in there.