King Arms P90 Upgrade

[crusty]

Just after some advice & opinions if possible,

I have a King Arms P90 that i am looking to slightly upgrade, i have put an 80mm suppressor on it so with the standard inner barrel length of 247mm + 80mm suppressor length am looking at up to about 327mm inner barrel length, i was wondering if the Massada barrel at 318mm will fit ? also what hop & spring would be best suited to run up to 350fps ?

Thanks in advance