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If you're after RPMs I'd go with a destroked 2.5L (2.34), those rev to 9K if you use the right internals - IMO this is THE engine to have if you're building a 818-R. If I remember right, it's a 257/255 block with a 205/207 crank and custom rods. There was a group buy for the rods and pistons on NASIOC not that long ago, I'm not sure if it's still going though.
I spoke with someone at Maxwell Power (http://www.getadomtune.com/services.htm) about the 2.34L engines, which they build in various states of tune. Expect to spend $5K - $10K, probably about $8K for what most people would want for the 818.
Oh yeah, having MPS do it isn't going to be cheap but they do good work. I briefly considered making a 2.34 after I bought the case halves from an EJ255 to make my 205/257 hybrid. It wasn't going to be all that much more than buying the forged internals that I'm looking at getting now. I'd have to check NASIOC to see if the groupbuy is still going but I want to say it was ~$1500 for the custom pistons and rods.