The 6" MC has a bore of 25.5mm and a stroke of 34mm. I measured the one I pulled from the 94 (I knew I wanted that for a reason besides just the res).
Giving it a surface area of 80.110612666539727580797406273627 square mm'*,
and a volume of 2723.7608306623507377471118133033 cubic mm'*.
Assuming the the 8" MC has the same bore but an increased length stroke, it'* got an 84.8mm stroke. By that reasoning it'* a got a volume of 6793.3799541225688988516200520036 cubic mm'*.
That'* a difference of 4069.6191234602181611045082387006 cubic mm'*!!