B&G no longer make or support the
Network instruments, so you will have a difficult time replacing these displays. The B&G depth and speed transducers are standard airmar transducers, so you may be able to
salvage them with a different connector. You will not be able to use the
wind instrument with a different display. The
Raymarine type 2 drive can be used with any
autopilot, but you may have to buy a different specific
rudder reference unit for the autopilot.
The Furuno 1622 is no longer made, so you will also be challenged to find a replacement display unit. The GP31 is a contained unit and will need to be replaced as is if you need a new display.
Frankly, if you are going through the trouble of finding replacement displays for all of these on ebay, etc and are going to put in new AIS and
chartplotter, I would simply start all over and run a N2K network and get new
gear. I suspect the cost of all new
gear will be within 25% of the
price of hunting down old displays and setting up a mixed network
environment with the new gear.
Mark