I put down 585 on stock sticks and an arson kit. Added 90's and rail would never recover. So, This is about in line with the 600hp theory that has been around for the past few years. Mostly depends on the health of your pump. So if your going to shoot for over 600 skip the bag o parts, save your money and buy a modded pump. As far as the best or economical cant help you there. But i will say i bought a 3.5 from John at Floor It. Ran the pump for about three weeks and it started leaking fuel. Sent it back and had a new one in three days. Turned out that the pump body it self had cracked internally. So it really boils down to customer service, since they all cost about the same and I have seen no Proof that any one is better than the other. Call them all and go with the one that gives you the good vibe.
