Borg Warner efr on twin scroll manifold would be my advice, go as small as you can as long as twin scroll. We aimed for 400 on mine and got 469 but on low boost map it still does just over 400 and feels great.

If you don't have straights then thenclose ratio box works really well, I have oppliger long box close ratio on 3.9 diffs and it feels great, I wonder if that would be better than the turbo to be honest. Mine is 4x4 though so not sure what you would do on 2wd but the standard cossie has long gears.

Depending on map and turbo 400 bhp comes with a lot of torque.