A few months ago in our March '09 issue, I introduced the 5.3L LS Chevy engine I was planning on dropping in my '72 C-10. For those who missed it (you may need to find a back issue to get up to speed) ...
There are lots of engines available to stuff in your 4x4, but the small-block Chevy has never been surpassed as the hottest engine swap ever. With the Generation III and IV engines (aka LS Series) ...