Originally Posted by americanyouth
Here's what I'd do if I were you; swap the 2.5 shortblock in, and leave your 1.8 heads, ECU, intake manifold, etc. This will increase your compression ratio, you will need to run higher-octane gas, but of course, you will also make more power than a complete EJ251 setup.
The real reason why I'd recommend this setup, though, is because it is cheap and easy. With a couple helping hands, you could do a shortblock swap in a day. There's no wiring, little downtime, and the process is well documented on NASIOC. A EJ251 shortblock should run you around $300.... PM me if you're having trouble finding one.
What sort of power would I be looking at? I'm sure that I could find a shortblock relatively easy. In fact, I found a complete 2001 2.5 engine w/55k for little more than $500. Also, what would my CR be? anything else I should know?