IO 540 / 2300 SFRM- What option is best, new engine, overhaul or remanufacture?

Is there anything wrong with it? Does the borescope look good? Oil analysis? Does it burn oil? Has it been flown regularly? If all's good, Mike Busch would say to just keep flying it. That said, determining how long you're willing to wait might be a big determining factor of which way to go. Some big overhaul shops and the manufacturers can have long lead times (like, months+). Minimizing downtime might be one approach (like, ordering new or an exchange and flying it as is until it's ready), or if you want to prioritize saving money, you can do an overhaul but it might take a while.