450 is no hardship, and certainly does not need 35psi or 6.2CR.
The turbo choice is you MOST determining factor, once you know your bottom end will take it.
Personally I would mod the head with a DE SHROUD, as this will bring in boost a LOT lower(500-800rpm lower) and hold onto it a lot higher, about £280.
I would lower the CR a little to run a bit more boost, about .4 lower.
I would use a T38, and ecu aftermarket ECU , as the 3 door one is crap, you might as well go CL+EGT if doing this, for power and economy, I recommend Emerald, and is what I use.
You can chip your existing ecu, but when adding CL, AL, Coipack etc it is much more expensive than aftermarket one that is loads more powerful and better, and user friendly.
It is a bit too much to go in to here but, these are some of your main considerations.
tabetha