372or 416 and why

yup, 240's basically a modern valve job and some cleanup. But RPMs will move that out of the box when you fix the valve job, for about $400 more at my shop. I'll take the weight and better chamber for that $400. And the 500hp will be made much lower than 340's peaks regardless of the stroke. The 4" engines I've played with having good to really good RPMs will pass 500hp around 6K, with peak torque in the 4-4300 range. On pump gas. Very streetable.