Two ways
Jeff,
There are two ways commonly used to stroke a 351W. The old way was to use a 400 Cleveland crank machined to fit the Windsor block. Special pistons are needed and the block must be clearanced to allow the rods to miss the pan rail. Displacements run as high as 430 cubic inches. Stick with around 408 CI for an engine that will last a while. The piston skirt gets really short on the bigger versions which gives poor ring sealing and short engine life.
There are now available new cast iron and forged cranks for this mod from several aftermarket companies because 400 Cleveland cranks are getting hard to find. This is not a job for the corner machine shop, I recommend you buy a complete short block from one of the many companies that specialize in stroker kits to save money, time and heartache. Coast High Performance in California has these short block assemblies for around $2500.00. It's a good deal and you won't regret dealing with them. Ford Racing Performance parts has one available too for a little more.
Royce Peterson