n47 head
 

does the n47 head have square exhuast ports or round. I am looking to swap to a L28 engine but not sure about the exhuast ports on the new head. will I need a new exhaust header or not?

Well, this guy's page is usually a really good guide to the spectrum of Datsun L series heads:
http://www.geocities.com/zgarage2001/z.html
and he says the N47 has the diamond-shaped exhaust ports.
I just last week took my intake and exhaust manifolds off of my '78 L28 in preparation for getting the block cleaned for a rebuild. It does indeed have the exhaust "liners", and by year also should be an N47, but I remember looking at them and thinking "square", as opposed to diamond. I'll look again tonight as I have to get the left side freeze plugs out next anyway.
Given you've got a '71, I'd say you're looking at a different exhaust setup. Of course, if your donor L28 comes with an exhaust manifold or a decent header, then you're all set. As long as you're going to all this trouble, though, it sure is a good time to put on a really nice exhaust... aside from the money, of course.
good luck,
Dave

use the head from your old engine on the l28 block if you have it. Anyways, the square exhaust ports flows better then the round ones on the n47