Making power out of the 318
The only bore size that has a major limiting effect on high ish hp like 400 + hp is 273s 3.625" bore, And yet the bore is still big enough to satisfy the average performance enthusiasts, if they choose to build one.
And a 318 bore is .285" larger than a 273, a 413 has a bore size that is closer in size to a 318 than a 273. 318/360/340 are all in a similar bore size ballpark.