I just installed a LS in my Arntz. It worked quite well. Do you have front bracketry? If not, this place has some great pieces for cheap.
Ictbillet.com
I bought the engine mounts and the bracketry to mount the alternator on the lower drivers side. Everything lined up good. I also had to go with a Corvette
oil pan due to ground clearance. The pan on the crate engines is deep and say about 2.5" below the frame. I had custom headers made at GP headers. They fit perfect.