Thorley had made some improvements in their Long Tube Headers for the 4.0L.
They have a larger primary tube now, 1 5/8" up from 1 1/2".
The tubing is now 304 stainless instead of mild steel. Flanges are still mild steel.
Still come with the bright ceramic coating inside and out.
I got them to install two O2 bungs per side. The normal location in the center primary tube is still there. I got them to add a second one on the collector. You can screw a wideband sensor in there if you want, or you can get an extension harness from URD that will allow you to relocate the front O2 sensor to the collector. This is good for people running the X-1 so it will sample the AFR from all the cylinders under power for controlling the fuel mixture instead of just one.
These improvements have caused the price to go up. I still have them on the URD site at $515 but will be going to up to $545 next week.
I just got a big shipment in and can ship right away.
If you want to get a set before the price increase act now!!