Although i havnt finished with my rb20det 280zx im already thinking about the next project.
Im seriously thinking about putting a built N/A rb30/25 into a 240z.
I was reading a zoom article a while back about building an n/a rb30/25. according to them they achieved a 32% power increase from just the head swap. that would equate to roughly 150kw at the fly from a stock 114kw rb30. Thats in the same region as a standard rb30et without any work just standrad 25 head on 30 block. not too shabby. Then think about upping compression, full engine balance, porting, cams, management etc.... I dont think 180rwkw is out of the question.
id love a balanced NA six pot capable of 12 or 13 second passes.
Take a look at this 240z vid. 3.1L stroker with triple carbs making 320hp.
http://www.bbgraphics1.com/73z/strokervideo.mpeg