Another option are PEMs, much lower price, they bolt right in without modifications. Rockers, Springs, and pushrods are a good idea if you really want to open that engine up. Forget the pulley for now. If your going to drop it, only go to 3.4" and do that after the scan gauge. To go lower then 3.4" you will need to allow the engine to breath. The exhaust mods, and rockers will do this. Changing your manifolds will take 4 to 5 hours, and a LOT of frustration.
You'll carve up your arms, and will not have a great day. Rockers/springs/pushrods will take 5 to 6 hours. Is not as hard as you may think. Go slow and it will go well. As long as you dont drop a keeper down in to the engine.