Miami B03

I was hoping someone would help here. I'm about to get a Silverado 16 or 18. I thought you are visually able to tell the 153" wheelbase. However, when I vin check this truck it appears it is a 153" wheelbase even though it looks exactly the same as another truck. Unless they have the vin incorrect. It was my assumption all 153" wheel base silverado's or all trucks for that matter, the increased size can visually be noticed in front of the rear wheelbase. Also, aren't all 143" wheelbase the short bed (5'8")?