Will a 250 cid cyl head work with your 200 cid ford engine?

It'll bolt on but there will be compression ratio issues. If I remember correctly the 250 combustion chambers are considerably larger than the 1960s 200, so the compression ration will drop a lot. To restore a decent compression ration you'll need to cc the head, do some calculations or look them up in a book devoted to rebuilding Ford inline sixes (there are a couple available via the web), and decide whether to mill the head and/or block. Hope this helps.