By 5/8" VHF whip did you mean 5/8 wave? They aren't 5/8 wave VHF, they're low band VHF unity gain antennas for the 42 MHz radios. You can tell by the low band matching coil bodies being much taller than a VHF high band coil. Those antennas aren't nearly as efficient as a low band 1/4 wave, but they make the cars look "prettier." All NCSHP cars still have low band radios and will continue to have those until VIPER is fully built out, so that's probably a low band antenna you saw. The high band repeaters still in service will most likely have ~18 inch 1/4 wave whips instead of 5/8 wave gain antennas.
NCSHP dispatch is a multicast on VIPER 800 and low band systems. Be aware that with most of the cars being equipped with VIPER mobiles and the troopers having VIPER portables, VIPER is the primary mobile radio system now in most of the areas you will pass through on I-95 and there's not a lot of low band mobile traffic anymore. Monitoring the low band side of NCSHP radio will leave you mostly hearing the dispatch side only and no mobile traffic for two reasons: the low band system uses non-repeated semi-duplex channel pairs, and the trooper is probably using the VIPER radio instead of the low band. Check the database for the low band channel pairs if you want to program your radio for those, but don't expect to hear much out of the low band mobile side unless you're fairly close to the mobile that's transmitting, if he's actually transmitting on low band, that is.