E,
All 2nd generation trucks came with rear-wheel ABS. The 4-wheel ABS was optional.
My 2000 truck has a sticker on the inside of the glove compartment door that lists some (maybe all) of the options it came with. The code "BGK" is shown as indicating 4-wheel ABS. Your dealer should be able to tell you whether or not your truck has 4-wheel ABS if you give him the VIN number.
Both my trucks have the 4-wheel ABS, and both of them exhibit ABS engagement when I slam on the brakes in the snow. I don't know how the rear-wheel ABS trucks behave.
Loren