https://www.electro-tech-online.com/custompdfs/2004/03/8085_datasheets.pdf
This is the datasheet of 8085, and they show all the necessary component to get I/O port. Besides, you don't have to use any more components. Because, as I see in the project, it's enough to use I/O ports to control the robot.
In the program of 16f84, they use only I/O port to control the robot. IF you use 8051, you dont need any different components. Just keep the whole design. But if you use port0 of 8951 (the same to 8051) you have to put pullup resistor 4.7K to the port. Because 16f84 has its internal pullup resistors, but port0 of 8951 has not. If you use other ports of 8951, it's oki, just keep the whole design.