Supersprint system should be okay, but you need to be aware that this is mild steel and will rust. A better solution would be to get a custom exhaust made.
An alloy radiator for that power, it isn't necessary. Same as uprated alternator. Why do you need that? Several coupes with 400+ BHP all run the same standard alternator. If it's dying, then get it replaced.
Does the exhaust manifold need doing? Would be worth checking if it is cracked and it will be a far easier job to replace with the engine out of the car if it is cracked.
Your car is Usain Bolt with wellies