I hope I'm not being too dumb here but I just want to be sure. I have a 1999 S2000 and currently looking at getting a new engine. A 2004 facelift engine has popped up but unsure if it'll be a straight swap.

Any help appreciated

 

Direct bolt in, with a tiny/simple fuel line mod by the fuel rail. It will be obvious.

Your biggest challenge is redline, the 2.2 is safe to 8400.