You can do this with one external 4-bit-to-7-segment driver circuit, and four MOSFET transistors.
You need to use 7-segment displays with common cathode. Each of those cathodes then go to a separate N-channel MOSFET (such as the BS170.) The gate of each of those MOSFETs then goes to bits 4-7 of the output port, to serve as "segment select."
Then, bits 0-3 of the port go to the LED driver (like a 4511 based IC) input, and the seven output segments go to the anode of all of the segements.
Then, you set up the code to drive the LEDs at a 60 Hz duty cycle (times 4, so 240 Hz interrupt rate.)
Each time you get the interrupt, set bits 0-3 to the value of the next digit, and set the one bit of bits 4-7 to select that particular output digit.