do I have a full floating rear end on a 2000 k/2500 3/4 ton chevy pick up truck it has a 5.7 vortex engine in it?

it is a full floating since its 4x4

Not necessarily, it's probably a SF (semi-float) rear end if it's a 90s model. Easy to tell by looking at the pumpkin: 14bolt SF is rounder, 14bolt FF is more angular and has another set of bolts inside the wheel lugs, at the end of the hubs, which is what holds the axles in. The Semi-floater is like a half ton in that it uses c-clips to hold the axles in, but is still a beefy rear end with ~10" ring gear.

here ya go "if" you bolt the axles into the outside end of hub they are floating axles. vs removing diff cover and pin w/ c clips.

some 90s model 2500 had a 8 bolt 115mm rotor on early, late models were I believe 135mm. there were 2 different sizes.