How is it hard to make a 340 run? Doesn't the OP already have the 340? I have 3 blocks sitting in the shop. They aren't that hard to get. They aren't 50 bucks like 360... Oh wait I don't see many 50 dollar 360's out there. We must be talking 318 now. My point is the 360 isn't all that. Until the stroke gets up over 4 inches. Then you need the bigger main bearing for more over lap. Oh wait. The 340 main is big enough to handle a 4.125 stroke at least. Yet the 360 is still hampered by bore. The first thing you learn about air flow is don't crimp it. Want your heads to flow better? Use a bigger bore. That's why many people don't see an improvement using 2.02 valves.