It's been mentioned elsewhere but neuroplasticity means it doesn't matter about 'matching up'. The problem is making the connections stick and regrow. At the moment we can't do this with the spinal cord. Peripheral nervous system nerves regrow if they are lined up correctly, although the fastest speed they will regrow at is 1mm per day. even if you could get central nervous system nerves to regrow like this you are looking at around 4 years for the average person to regrow the nerve to move their big toe (around 1500mm from base of spine to toe). Then you need to ensure that the sensory nerve roots, which have their nerve bodies in the dorsal root ganglion of the spinal cord, will grow up to the brain and integrate in the brainstem with the ascending 'last leg' nerves.

Other people are talking about glues and other substances that may speed this up (ie instead of requiring a nerve to regrow it could just attach to the other side and start working, like having a set of ethernet cables from the brain and just plugging them into the other side) however they are all just as experimental as the general concept of removing and replacing a head as far as I can tell

That's very informative, thank you.