square header on round port?
 

I know this sounds like the most ridiculous question ever, but can you put square port exhaust headers on a round port head? This guy is trying to sell me some nice headers, but they are square ports. He said that he used to run them on his N42 head w/no problem, sounds a little fishy to me. He wants $125 for them, barely used. I've been hunting around with no avail for mine, not brand new I mean.
Not totally on my subject line, but can I expect any increase in performance going w/headers, 60mm tb and a cold air intake?
Lastly, what type of exhaust setup should I do? I was just thinking of "straight piping" it out from the headers...too much noise? Should I do a muffler set up, I don't think so with the headers though, defeats the purpose to me anyway. Is there anyway to squeeze dual exhaust in the back?
Sorry about the long post, need to pick the brains of the experts.

First off, an N42 is a square port head, the round port was introduced on the N47. Regardless, if it was me, I'd give it try, but only if they were dirt cheap. Which in this case they're not, so I'd hold out. I know I've seen many round port ones for sale in the past. Maybe its because the owners upgrade to a square port head?

A straight pipe will be WAY too loud. I used to work sound control with the SCCA, and the Z's with this setup wouldn't pass the 103 dB limit at Road America. I'd go with a flow master, or something similar too. A 2 1/4" single pipe seems to work best, which I had on my last Z with MSA's 6-1 header. This setup with a muffler will make just as much power as one without. I've heard of guys complaining about flat spots in acceleration with the 2 1/5" setup. A dual exhaust is a waste for a street car.

Sorry, I did mean N47. Thanks for the advice on skipping the straight piping. I was just trying to save a few bucks was all, call me cheap right?

Some more questions now: I can get the MSA 6 to 2 to 1 headers for a decent deal, but the thing is he's missing the 2 to 1 flange. Will they be able to sell me just that part from MSA you think?
Second, mufflers...anyone have any recommedations? I've heard some things about Monza and rusting out quick, any opinions? I really like the way the 240 or 260 one's look in the Victoria British catalog with the 2 vertical pipes.
I've seen some decent dynomax one's too. The thing is I don't wanna sound....um...ricey is the best word.

HELP?!

hey, I'm thinking about the same thing. I had my eye on the MSA 6 into 2, with the 2 into one connector piece. They do sell it seperate, you just have to either a. call them, or b. find where it is on the menu. I have a question as well. The exhaust on my 240Z is all rusted, and I've got cracks here and there. Right now, I have the stock exhaust, but it has a melted down glasspack (my dad's craftywork) as the muffler. I like the sound of the glasspack (it sounds mean, but not too deep), and I was thinking of getting some headers and a new flowmaster muffler. I don't want anything that is going to make my car sound like a boat, but I do want the increase in horsepower. Based on what I said, should I go with headers, or should I just get the stock exhaust redone? Thanks for the help!

This is what I have done to my 78Z. I still have stock exhaust manifold. I am running a 21\2 exhaust with no cat and a flow master muffler. The sound is awesome but gets tiresome on long drives. I find myself changing speed from 60 - 110 so i can have different exhaust notes. Otherwise it is a great system doesnt sound ricey at all. It almost sounds like a nicely tuned IROC.

I originally had a stock manifold with a 2 1/4" exhaust and a flowmaster, and was happy with it, but the headers did make a difference. It was a bit louder too, of course. Also, I feel the Flowmaster sounds better than a glasspack. Either way, the exhaust did become tiresome on long trips as well.