The cylinder bores of the later blocks are longer than in the early blocks and the crank throws are larger on the early cranks. Hence the need to clearance when using an early crank in a late block. The longer cylinders of the later blocks are often preferred for stroker builds when using a 4.3 stroke crank or bigger because they offer more support for the piston at the bottom of the stroke.
Also, there is an oil slinger/deflector on the early cranks which is not compatible with the later blocks and needs to be ground down.
Externally balanced 4.14 cranks are readily available and as has been stated are fine for anything outside an all out race build. You can also offset grind a factory 460 crank to a 4.14 stroke. Externally balanced cranks are easier (cheaper) to balance as well.