if going down this road, why not get two kawasaki h2s, bond them together, they were an old 3 banger two stroke from the seventies. could get to around 1400cc inline 6 and it would be a two stroker and would sound wicked, and would have some major power potential, plus the blue smoke rolling out the back would be a blast.
alternatively a couple of rz 500s would be cool, v4 2stroke water cooled engine. this would yeild a scary sounding 1000 cc z. hell while we are at it just get 3 banshee engines, put the 750 cc big bore kit on em and go to town. 2250 cc inline six mean machine. someone do it please.