With dark greens, do you mean 803’s? Those are capable of 340-350 bhp. With Siemens 55’s you will be able to go over 400.

Turbo wise there are several options. A T34.63 will do close to 380-390, and a T36 and T38 should go over 400. But they will be very laggy. Another option is a GT3071 which is more modern so will be less laggy with good power. As said the Borg Warner EFR will be best but requires a special manifold.

Cams are not needed for 400. My preference would be a modern turbo, but in the end I chose a T34.48 as it meant I could have an off the shelf chip, which is a lot easier if you are in Europe and all the good tuners are in the UK.