I'm guessing the Z's are forged. Anyone know for sure?

 

AFAIK, they are not forged. Just cast, though I am not 100% sure. I really don't think that anyone is 100% sure yet.

 

aluminum block and heads, forged crank and connecting rods, and moly-coated pistons

Your guess is good as mine..Most likely forged

 

The pistons are cast with a moly coating on the thrust face.

VQracers post on the Mines complete engine gives the clue

 

They are probably the high pressure cast type of piston common to Japanese motors. Extremely strong with very good control on bore fitment. Only thing they really don't like is spark knock, it has a tendancy to breakdown the ring lands area.