early 90's had a c30 motor
late 90's they introduced the c32 motor
i would go for a 98 b/c the c32 motor is more displacement && the rev limiter is 500rpms longer which increases vtec range. ALSO in the late 90's the final gear ratio was improved for higher speeds
if you find a nsx auto it's better to do an auto to manual swap b/c auto's weren't abused as much as manuals