Pulley Dimensions?
 

What are the dimensions of the upper and lower blower pulleys on an 02' Lightning and do you measure them from the outside edge of the pulley. I just bought this truck used and the boost is 10 lbs. I thought that 8 lbs. was the max. The truck appears to be stock.

The stock gauge isn't very accurate and the boost you get will vary a lot depending on weather conditions.

The stock crank pulley is 7.5 inches and the stock blower pulley is 2.93 inches. As mentioned the factory boost gauge is not very accurate.

Do I measure outside edge or from the grooves of the pulley?

From the outside edge - the lower is 7 7/8" , the upper is 3 1/4. The lower is most commonly changed. And yes the factory boost gauge often reads to 10lbs.
Hope this helps.