Torque is definitely low for that number. Some more aggressive negative timing on the exhaust cam should bring that number up significantly. I made 405/400 with just a tune and intake, but on 93 octane. So you should be able to squeeze out at least 390ft lbs.
As for the spark plug question, I swear by NGK iridiums. Burn clean, strong spark, and last a long time. Work with na, nitrous
(some people will disagree), and with forced induction (with the right temp range of course). Also they're usually cheaper than the boutique plugs like brisk, et al.