Re: 3.9 TO 4.2
Well for all the stuff you need talk to Tom over at Super Six Motor Sports. he has everything that you will need to do the rolling assembly upgrade. But i definitely don't think this is a plug and play job and can't be done in one night. Best to send the engine out for machinin, honing, etc. i am not sure of the increase in HP but Tom would be able to fill you in on those numbers if you call him. good luck with the upgrade.
3.8L with Forged and Balanced Internals,65mm BBK Throttle Body, JBA Headers, Mild Cam, KN CAI, Port/Polished Heads, T5 with GT Clutch, Steeda Short Throw Shifter, 180rwhp/200rwtq, Foose Df-5 18", 14" Roush Alcon Front Brake Kit