This is for 340 builders

the 340 steel cranks had the center of the rod end board out to make that end lighter. I beleive that would give you quiker response and require less weight on the outher end to balance it. ill bet if you bought an after market 340 steel crank it would look exactly like an old 318 crank. i have a 340 with an old 318 crank in it and it loves high rpms with no problem at all. I am not a moter builder but thats what i learned when i put mine together.