Yeah, I'm a CA18 guy through-and-through. But for a hardbody, I don't think it's a great fit. You really have to rev these engines to get them to make power, and with a truck, it's an odd fit. Also, all of the "normal" engines are so old at this point that the engines probably all need rebuilt and the wiring is old and crusty, so I'd plan on a rebuild and standalone. If that's not in your budget, it might be best to rethink it.
I'm with dash on the engine as well. The VG30ET would be a great fit for a hardbody. Smooth, and plenty of torque. Still probably going to require a rebuild and standalone to make it reliable though, but it wouldn't take much to get it to walk all over any SR/KA you ran into, and would probably easily hang with any mild LS swap you might run into as well.