I can't really see why you'd want to use external counter ICs when you've got a microcontroller!?
As Felix has already mentioned, the 8051 has dedicated Timer-Counter hardware built-in.
Simple counting (as in a counter IC) in software is trivial.

Could you explain further why you specifically feel the need for external counter ICs - very high speeds, perhaps?

Or is this just an excercise in gaining familiarity with counter ICs - in which case the microcontroller seems an unnecessary complication!