Look for a CB60 apart from cb23 as well. Back in 2007, there was already a shortage of CB engines in second hand market. I'm not sure if you will find one in good condition.
If you do find one, there would be nothing like it. I know this car inside and out and will be able to help you with a lot of things. If you do have to swap, go for Toyota 2E engine. It's a carby and fits with minimal modifications to the mounts and axles.
Keep us posted.