I have 1-3/4" header tubes, but that is because 1-7/8" would not fit on the car. In an Arntz, the engine sits way back and the bends were too tight.
I made a block that fits between the header flange and sidepipe for the O2 sensor. I put in 2 threaded holes for the O2 sensors. One for the narrowband included in your kit, and another I use for a wideband, which can be plugged off. Works quite well. For my headers, I cut off the flange where it mounts to the head on the original SBC header. I bolted a piece of steel maybe 18" x2" x 3/16" to the LS3 head after I drilled the mounting holes. I welded the old header to the piece of steel mounted on the LS3 head. I sent this set-up to GP and they fabricated the headers from there. They fit perfect. I also had them shorten them by 1" so I could install the block I mentioned above for the O2 sensors.
I did not have room for the batwing
oil pan. Here are a few sites showing the dimensions.
http://www.stevesnovasite.com/forums...d.php?t=208618
LS SWAPS: Oil Pan Guide
There is a new aftermarket pan made by Mast I think that is real shallow. I think you have to run the
oil filter in a different location due to the depth of the pan. The F-Body pans are real common. Corvette C6 LS2/3 pans not so much, and batwing pans are somewhat hard to find. You can find them if you look on ebay
If you buy the ICT billet stuff, I had to use 3 separate "kits", but I think they put them all together in this kit. This is almost exactly how the front of my engine looks:
LS1 Alternator Only BELT & PULLEY LSX LS Power Steering Delete 551550
The upper left is actually the belt adjuster. This kit is for a LS1. Not sure if it fits a LS3 or not. They are great to work with on the phone.
For the T56, I had one from a GTO and had to move the shifter to the center. Are you sure you do not have a T6060 trans? I think they have a center shifter available already.
If you haven't been there, go to this site. They have a lot of good info on the pans etc.
http://ls1tech.com/forums/