I was thinking a 221 crankshaft in a 250 block would be an interesting combination. The I realized a 221 crank is probably more of a fit in a 200 block because of the crank nose similarities.
I am not building a 200, but if I were to, I'd be looking for a 221 crank.
As far as the Header question, I asked the question, then found a post that I had posted earlier asking the same question.
Ken