i dont think the 750's are networkable in the true sense of the word but we were running 2 x 750s on a NMEA 2K system and they would both repeat all information and work independantly of each other.
We were running engine data through the can bus interface, depth sounder, ais and usual chart plotter functions.
Didnt have radar but would think they had radar input, in which case i would assume the one with the radar feed would show the radar data but the other one would not?
Would they not be a bit small for radar overlay??