Okay, I have an answer now. I took a stock flywheel from a gx 340 generator and set it on my gxv. It fits fine. BUT, the ring gear is NOT the same. So I wud have to say that yes the arc big block flywheel will fit BUT u would have to mount your original ring gear to it in order to still have electric start. I don't know if that's possible but I'm sure arc could answer that question.