Ya I agree with you on the change of heart, just made the same decision myself. Sadly if you want 400 hp to the tire your most likely going to have to stroke the engine. I have been checking out the FRPP BOSS Modular block for my build when the warrenty goes out, they say you can bore and stroke it out to a 336 which I think comes out to a 5.4 or so. The shop that I spoke with said I would see about a 60hp increase with the heads and cams. Comp cams claims you will get more hp with the spings and phaser mods, Personally I would do them since you will be in their anyways with the cams, but that will also increase labor costs. I believe Brenspeed sells a n/a cam with good #s without changing the springs or phasermods if you decide to go that route. Livernois and FRPP sell some nice sets of cnc heads if you havent looked at them yet.