Dan, nitrous wont effect the injectors as it will be a wet kit that you use (if you dont i will personally come round and insert the bottle in you) so it will take care of its own fuelling.

Greens (803) will manage 350bhp but only at slightly higher pressre than the cossie lads run, but thats not an issue to you if you use a decent (044?) pump.

Personally i would use some siemens injectors though, 100 quid a set stateside for some 500-550cc ones which means they will fuel 400bhp+

They open and quick so fast you can still have a lamda sensor and silky smooth idle too