first off, if it is truely a stroker it will have to have a plate under it or cut domes.
i guess you could machine the stock head, but i would just a head.
bore that bitch out, dont bore it if its over 80 thousands, usually if its a 4mm you have to run 795 pistons they come in 20 thous overbores. so has to be 20, 40, 60, 80.
then get with david noss and get some cut domes for a 4mm stroke would be the best guess.