I assume it is part of the vin but what is a B4U package?
Actually B4U is the Sport Performance Package and V92 is Trailering Provision.V92 is the 'trailering package' option.
B4U is the 'sport suspension' option.
Both required, among several other things, the LT1 engine. I'll admit I've never personally seen one without the other, but they are two different things.