That's an open question with so many variables and not what the OP asked but I'll humor you.

What is the car going to be used for? What are the power goals etc?

Obviously the easiest way would be to build a 257. Again how far you go with that build depends on the answers to the above questions.

Mild to Moderate power a well built 2.5 is hard to beat for an all round / fast road / occasional trackday car. However if you want big power it's not the platform to start with.

Lets look at mine for instance. I've done everything I can to mitigate potential failures. But the truth is I'm expecting issues when I start to push it properly . I wouldn't mind betting that I get a dropped sleeve at some point. Even though they are Darton top hat flanged sleeves I still know of several engines that have had these and have still dropped. So it does happen. The BC Racing UK Time Attack Car I was pit crew on was one of them. The EJ257 got binned in favour of a stroked EJ22T. It made a massive difference to the car more power and revved like a bastard.

For a big power build the EJ257 is not the platform I'd use if I had the choice of them all.

Take a look at Roger Clark Motorsport's Gobstopper 2 for example. That's an MY08 that came with a 2.5 out of the factory but what do they use? A closed deck 2.0L and there's good reason for that.

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605whp
Quarter Mile in 10.9 seconds @ 135mph /217kph
0-100 kph 3.2 seconds