Oh dear God! 318 stroker

4 inch crank in 318 block get an off the shelf kit and probably cheaper. 4 inch arm is like a long wrench compared to a short wrench - more leverage - more torque. And 4 inch stroke has shorter lighter pistons which makes them rev a whole lot faster. Its the hot setup for small block mopars they drop right in no special machining required. Make big block torque without the size and weight of a big block.