The diplexers will work both ways. https://www.theantennafarm.com/catalog/comet-cf-4160j-1638I think you want a duplexer not a diplexer with a dual band antenna.
You use a duplexer to connect two radios to one antenna. You use a diplexer to connect two antennas to one radio.
A properly installed NMO mount does not impact resale value.Thank you for the help. I don’t wanna drill for resale value of the vehicle.