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So, I'm almost at the point where I could get some headers put on my car, I have all the tools needed where I work, it's just a matter of getting pipe and doing it. But first, a few questions. Specifically, what is there to be improved from the stock headers? Better flow? How? Also if anyone could give me ideas on ideal sizes, lengths and bends for fitting, I don't exactly have the time to leave the car inoperable for a week or so while I sort this out in my spare time... Thanks.

Hijacking my own thread here, but a few more questions. If the old exhaust is replaced, do the O2 sensors need to be the same distance apart as they originally were in order to function properly? Also, does it make a difference in sound if you have a short exhaust/long tail pipe vs a long exhaust/short tail pipe? To clear up any confusion, by tail pipe I mean anything past the muffler, and exhaust would be anything before.

1 5/8" primarys are what most have been going with.  Merging them on top of the trany to a flex joint is a good idea then feed the front banks exhaust in after the merging of the rear bank.

The upstream O2 sensor can be put anywhere in front of the catalytic converter. Since the downstream is for catalyst effenciency , I would keep it as close to the converter as possible on the downstream side. I'm just guessing here, but I could see the emission gasses changing do to cooler temperatures while travelling through the exhaust pipe that could give an altered reading? ÂÂÂ
Maybe you could research some catalyst equations and let us all know. ÂÂÂ

on the subject of header construction, does anyone know of a good pipe kit to cut/weld the primary's and collector.   Like the ones that just come with a bunch of pipe curls and the collector

Jegs sells some decent kits.  I wouldn't go above 1 5/8 inch or your velocity could drop way low on the exhaust gases causing backflow.  You can get 1 3/4 header plates and do a backflow ledge on them for the 1 5/8 pipes too to help.  For primary and secondary length get the equations and figure out the tuned length for best performance.

Check out my posting called "header pics" in the exhaust section. I used 1.5" pipe and placed the O2 sensor where it would see the two banks as well as possible. The header are coated in and out which helps in keeping the heat in, and the engine runs cooler as well!