I am looking for headers for 66 mustang 289 3 speed and want any suggestions on tri-y's or others that would fit good and are not much problem. Also looking for opinions on buying off e-bay (used) vs. New, and any suggestions for a good place to look for new (mustangs plus, etc...)
I'd recommend the Hooker Comps aswell, or the Super Comps if you have some extra $$. If your interested in keeping them looking nice, I'd definately go with a coated set. While my Comps still perfrom great, the paint tends to bake off a little bit.
I'd always go with either www.summitracing.com
or www.jegs.com
for any parts not specifically mustang related, for the most part I've found them to have a much great selection of parts, better quality parts, and MUCH MUCH cheaper.
Also keep in mind the different types. Shorties, Longtubes, tri-ys. I THINK shorties will give you more torque, while longtubes are better up top, but don't quote me on that, hopefully someone else will clear that up. Also keep in mind ground-clearance with longtubes...I have to go over every speed-bump i come in contact with almost sideways with my longtubes.
How far are you going to go with building your engine. If you plan on a beast then yes, I would go with Hooker Super Comps or Heddman Elites or something. However, if you are keeping it relatively stock (perhaps say... intake and carb, ignition upgrades only, maybe small cam, etc).. i would say don't go too extreme with the headers and get Tri-Ys or some smaller headers. Big headers on an engine not built for them will lose you power, since the advantage of big headers come at high rpms (rpms that a stock or near stock engine will never reach). Big headers also move your torque up (and sometimes out, again if your engine doesn't rev that high) the rpm range.
So, as with all engine parts, you must plan ahead. And as long as there are no cracks or holes or excessive rust on the headers, ebay would be fine.
Edit: Looking at your engine, I would buy Hooker Comps, not Super Comps. They'd match your engine well.
Depends on your funds, because Hooker Headers don't come cheap. If you're looking for a set of inexpensive headers, then Hedmann (model 88300 I believe) headers are hard to beat and are in the $140 range. I put a set of those on my daughters '66 coupe without any problem. I see you are located in Portland as well, which means you can easily pick up whatever headers you want through Baxter's (which is where we got my daughters).