Fooled me too.
Sleeve looks AWFUL thin...
Anyway. 74mm piston+76.7mm stroke=329.87cc. Or more likely, 74mm piston+76mm stroke=326.86cc, so +7mm bore, and +6mm stroke. Methinks the piston would freeport, unless it was a longer piston, then it would only hit the crank at BDC, so a longer rod is needed, which would need a spacer plate, unless the piston is designed for it. Know what I mean?
Also, ouch on the head stay mount.