This has been the holy grail for years.... true longtube headers that fit an LSx with an automatic in an FC, with little modification. stainless at that!
Today I helped install them on my brothers car. He has pics on his cell phone that he will be posting soon.
After some failed attempts, about a 18 months ago I started looking at these and started asking questions and trying to get measurements from the SSR community and was lucky enough to get pics and measurements of some Kooks headers bolted onto an engine on a stand, and had my brother take the gamble.... they sat in front of his car in a storage unit for months, unfortunately the project took a back seat until today. see this thread:
http://www.ssrfanatic.com/forum/f35/got-long-tube-headers-i-need-pics-48573/#post1067917Now, what are they? they're OBX-R (brand) headers for a Chevrolet SSR off of ebay.
NOTE: there are two sets listed on ebay(obvious by the pics) for the SSR, I don't know if both will fit, but these do. The easily noticed differences between the two are the collector flange- these are a two-bolt design
NOT the 4-bolt collector flange, and the tubes appear more intertwined,
not more parallel or straight as they drop. These are a knockoff of headers made by Kooks for the SSR, at 2/3 the price.... yes, Chinese knockoffs(hate if you want). They came with a 3" Y-pipe (that we'll be cutting up so we can fit them to a 2.5" x-pipe with slip-fit reducers).... search: OBX SSR headers.
edit: from the OBX website- part number 501-1317-2
http://www.obxracingsports.com/products.php?pk=1621#Cost currently is ~$550 shipped.
What modifications were needed? We had to dent 2 tubes (cylinder #8 to clear the frame rail, and cylinder #3 to clear the steering shaft, dent a frame rail on the passenger side(do it while the engine is out for better effect & clearance), dent the passenger floorboard, and cut off two unused tabs on the rear of the crossmember by the rear control arm mounts. My brother's car had previously had an LT1, and the passenger firewall had already been beaten for header clearance, you may need some clearancing there too, but it shouldn't be as much... ours being out of the way allowed the right side O2 sensor to ft easily. No firewall mods were needed on the driver side and the O2 sensor fits easily.
Installation- since we had the engine & transmission already in the car, we hung it on a hoist and dropped the front crossmember and took our time fitting them with multiple test fits. We also removed the coil packs for space, and with the crossmember out of the way, they drop in from the top easily. We are using a set of Pez (Ronin) motor mounts on this car, but they should also fit Grannies mounts as well. IDK if they will fit Hinson mounts, since they place the motor a little more forward in the car from what I understand.