Rod:

If all you are doing is powering the A/C with the second shore power circuit, this is what I would do:

Install a 30 amp shore power inlet next to the existing one. ABYC (and it is a good practice to do so) requires a circuit breaker within inches or so of the shore power inlet. So install a surface mounted breaker, near the inlet. Size it to protect the wire to your A/C, which is usually 12-14 gauge so 20 amps will work. Then wire the A/C power directly to that breaker. This is a pretty simple and cheap scheme. Its downside is that you can't power anything else with that circuit and you will always have to hook up a second shore power cord.

There are more complex ways of doing this that can avoid the foregoing limitations, but it is probably beyond what a simple forum
reply can answer.

David