72 350 emmissions help needed

[72stik]

My truck passed all safety (in NJ) requirements. The engine has 97,500 on the speedo. The engine looks completely original, as did the cab interior, so I believe the speedometer. The engine has new air filter, plugs, oil and filter, and runs and idles fine.
At inspection the truck registered 812 HC where 500 was passing.
It failed. My question is, what are the first or most obvious things to check, and what are typical readings, or readings that can be easily obtained assuming the motor is in good shape. I appreciate your help. Dave