Been considering this also (with turbo) and doing a load of research for my GF8 before i commit to forging the 2L RA block that is in it. Parents have had an H6 legacy for years and its still going after 350,000kms of abuse.
forcefed made 412kw with an EZ30r on 98 at only 20psi with what seemed like a very mild build for the power. (just pistons, rods, valve springs, retainers, injectors, Link G4). So they're definately a capable unit, the supertech parts are expensive, but so is a 400+kw capable EJ engine....
Took the idea a step further today and picked up a blown EZ30r for "research purposes". Would be doing the manifolds, wiring, engine build etc myself so want to know exactly what im getting into.