To use the LS273s you will need low power common anode displays as they can sink 8mA and source only 0.7mA You'd connect the data pins to a port (B), the clock pins to other pins (A0,A1) and /MRs to 5V. You connect the displays via resistors to the Q outputs and the common to 5V. To display a digit you place the (inverted) value on portb and toggle the relevant clock pin.
You would be better to just drive the displays directly with the 16F84 as it would be simpler.
Mike.