6.2L like all commie metric displacements covers a range [in this case approx 375 - 381 ci], not a true measured displacement. just advertising, otherwise the shitbox chevy 6.2 would have the same displacement as the HC 6.2, and all 5.0L motors would be 305's vice 302, 304, 305, 307, 304.5 [for the Studebaker fans], etc.
HC motor -- bore = 4.09", stroke = 3.578", so true/correct calculated displacement = 376.07 ci [or 376.068381146 for those who don't like rounding off]
Don't feel like looking up the gov't motors product, leave that for someone else