I am not 100% certain on this, but AFAIK, all aluminum blocks come out of the same mold. The iron-block truck a/c bracket will not bolt up to the aluminum block. You have to use the a/c bracket off of an aluminum block. The choices are F-body and Corvette LS1. The F-body alternator interferes with the steering box, so that leaves the Corvette accessories. Another option is to keep the truck Alternator/PS and buy an aftermarket high-mount a/c bracket and Sanden compressor (about $425). However, the compressor interferes with the overflow bottle which happens to be the mounting point for the ECM. Sure the bottle can be clearance and patched, but I just decided to get the Corvette accessories.

I bought the 4WD accessories with my engine, then bought a Silverado alt/PS brackt with a PS pump before I decided to go Corvette. Unless you plan to complete the swap in a few weeks, avoid all the headaches and extra wasted co$t and search for the Corvette stuff. I found everything I needed on C6 Corvette Forum | 2005 Corvette | Pictures | Photos | Forum | Forums. Lots of folks on there that sells used parts.