take the engine apart, then take the block, main caps and heads to the machine shop. tell them what your idea is and come up with a plan together. they'll either order up the stroker kit for you, or tell you which one to order with which pistons you need. once they get the parts, they'll finish up the machine work and you can put it together or pay them to assemble the bottom end and you can button up the rest.
in the mean time, they'll inspect the heads and tell you what you may or may not need in terms of parts and repairs. or, they may suggest somebody that specializes in cylinder heads.
somewhere in the midst of this, you'll talk about cam shafts. this will lead to deciding on what your compression ratio will be and will be dictated by your desire to run pump gas, what pistons cost and any constraints due to valve clearance and camshaft selection.
the number one thing on your list should be to find a performance machine shop who you can communicate with.