Under $4k budget build LA360 build

Shot peening compresses the grain structure of the metal, "pre-stresses" it and makes it more resistant to cracking.
A shot-peened crank will have tiny pock marks (as Rusty mentioned above) on the non-machined (counterweight) areas, just as if someone had pummeled it with thousands of tiny lead shot pellets...which is exactly what they did.
It appears the weakest crank of the 3 types (forged, cast and cast/shot peened) is the cast-only crank which apparently only left the factory in the '72 340 (now you know why I changed mine to forged). My sources list ALL 360 cranks from '71-'86 as cast/shot peened. Hope this answers your questions!