How large can the working die size in a wide PDIP package be?
It depends completely on:


Design of the package outline
Design of the package carrier
Whether the package carrier supports multilevel interconnect
Design of the package lead frame
Number of pins on the DIP package
Length to width ratio of the integrated circuit chip


So as it stands there is no way to answer your question as written. If you are curious about any specific package technology then go ask the manufacturer. Lead frame manufacturers are probably the best place for you to start.