Turbo choice is personal preference but a gt35 should meet your desired gains. Just work out what size rear housing for when you want boost to come on in the rev range.
My build has gt35 with 38mm wastegate, current rear of 1.06 but downsizing to .96
I too am aiming for mid 400's but I'm still a few months of from running so I can't really tell ya how it runs.
Hope you have luck with your end choice. Interested to hear results
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