What is the difference between a 318 wedge and a 318 wide block?

First of all there is no such thing as a "wide block" 318.

Chrysler corp made an "A block" engine that used poly-spherical combustion chamber heads and then made the "LA (late A) engine using wedge heads.

The blocks are near identical and have the same dimensions.

Ill-informed persons may have confused the Ford designation "Y Block" with poly head coming up with the misnomer WIDE BLOCK