Me and my dad just bought a 1975 Cessna 182P. It does not have Mode C or adsb and it still has the original cessna radios which we want to replace although they do work. We plan to use the 182 for cross country trips as well as to build time towards an instrument rating. I think a GNX375 makes sense for adsb and ifr but I need some advice on the radio's and mode C transponder. Any suggestions?