This should give you the technical details on dealing with NMEA0183 talkers and listeners.
Assuming upgrading the chart plotter is not an option, and without an NMEA
2000 aware CP, you would need a multiplexer and an AT10 (and Simnet power cable with terminator). Better check you have the rudder
feedback unit that hooks directly into the AC12 whilst at it or you may need to build a small simnet network which is getting difficult because, I think, it is almost obsolete which means you would need to build a small nmea 2000 network with the required simnet adaptor cables
If you're up for the challenge, a Raspberry PI with a couple of cheap
USB RS422 converters and a bit of fiddling can be configured as an alternative to a multiplexer. With this latter option you can optionally transmit NMEA data on wifi
and run a secondary PC based chartplotter
as well. It's also possible to allow this chart plotter to be remotely accessed from other devices like phones and tablets, too.