Quote Originally Posted by spawpoet View Post
...is the bolt diameter the measurement of the diameter of the threads, or the diameter of the neck or head of the bolt....
Threaded hardware diameters are the "major diameter", at the outside of the threads.

I don't know your "L" engines specifically, but unless it's got some kind of "never used anywhere else rod magic", the hardware is not interchangeable; you must use the correct fastener. You should also resize the big end when you replace rod bolts. - GA