The L-Star project is an open-source single-board computer design that uses a Propeller microcontroller to control a 65C02 processor. You can use it to emulate early 6502-based computers such as the Apple-1 or the OSI Challenger, or you can invent your own 6502 computer.
All the parts that are needed to put an L-Star together are available in through-hole packages, so you can build it on a breadboard, or on a Propeller proto board. Or you can order a kit on Tindie (click on the Tindie link on the project page), which has some extra features such as a 128KB static RAM chip and an expansion port.
OSI emulation: in APR 2017 post indicated would be adding use of serial port to PC. Still planning to do so? :-)