The GM Performance Parts 383 roller block crate engine with the Fastburn heads would be at the top of my list. Second choice would be one of the GMPP 350 roller cam engines. GMPP engines are priced right and the warranty alone would make me seriously consider going with them. The LS is popular right now, but bring with it issues that Roger noted. GMPP engines are basically bolt in and go and would be a great fit for your build. I would go with the vortec head, or aluminum head also. You can use both GM or Edelbrock intake on these heads. Edelbrock has a nice carb for the street. I would go with the v-belt setup, rather than serpentine, and spend the money saved there to get the vortec head long block.