Speaking from experience, the EJ257 block with the EJ20 heads can turn into a nightmare very very qucikly. 2 years ago I bought my 02 WRX, rod knock 3 weeks into it. Found an "EJ20 block" on craigslist went and got it. Turned out to be a 257. I at the time had no idea of what to do or what could go wrong. 4k dollars later. It runs. Be prepared to spend alot of money on parts and labor. Highly reccomend. JP pistons, made specifically for this motor set up, bigger injectors... theres alot more I cant think of now. But beware this is a big job.