I've been doing research on engine swap alternatives to the stock 3.3L V6. I just want to know some ideas of what engines would fit in a first gen Xterra. And I'm looking for the best engine for off road purposes diesel or gas. Curious to see if there are any good diesel options, again this is more of a hypothetical future thing but I need some info. And lastly, would the 2nd gen 4.0L V6 fit in a first gen??