Hard to answer without ANY idea what your car is, intended use, trans, rear gear, etc........BUT:
Ford Windsor (Im assuming you are talking about a Windsor) heads, even on stock engines, bite, for lack of a better term. Putting them on a stroker (unaltered) is like YOU taking the soda straw you are trying to breathe through and letting Lance Armstrong try to win the Tour De Lance through it :/
Will you see gains? Sure. What, I dont know...thats gonna be one seriously choked-off motor. At least home-port the stockers and get oversized valves, if nothing else.
Sources for stroker kits? Pick up any MMFF or other Ford-oriented Vendor-Orgy rag, they are like locusts. They'll all love to sell you one...cant swing a dead cat without hitting a stroker-kit vendor today

I hear good things about adperformance in Cali, and Keith Craft Engines in AK has a sterling reputation. But Im sure others can give their recommendations as well. My kit was from Coast, and Im satisfied, but some others arent happy with CHP, so they will have to fill you in if they want *shrug*