Any reason why these won't work on a 4WD?

http://www.ebay.com/itm/OBX-Racing-Long-Tube-SS-Exhaust-Manifold-Headers-04-10-Ford-F-150-5-4L-V8-2WD-/191262177840?hash=item2c881d3a30&vxp=mtr
The 4WD version is $300 more and comes with parts that I don't need (flanges, resonators, and maybe the pipes).

I was going to have a muffler shop cut out and weld in new high flow cats and do either a SI/DO or DI/DO anyway so why not just let the shop take it from the headers on and work around the transfer case?

I guess most of that $300 extra if for the mandrel bent pipes. Would they make that much of a difference vs the shop bent pipes since I'm not dealing with a high performance motor?

 

Most of the time it is due to the collectors being longer and not having enough Y pipe clearance for the transfercase.

 

Good call. That's about the only thing that makes sense. Comparing pics, that 2wd collector does look longer. But, it also looks like there's room to cut off 3-5" if necessary.

Comparing the newer model OBX 2WD to the 4WD, the headers look exactly the same. The only thing that's different is the drivers side resonator and pipe.

I did ask the seller why it wouldn't work for a 4WD and they said "Because the manufacturing company designed it for only 2WD. Thanks". SMH

If all the manufacturers had different models for 2WD and 4WD it would make sense that there was some significant difference. I didn't check every single manufacturer but the ones I did check, Pacesetter, Stainless Works, and Dynatech, all use the same exact headers for all 04-08 5.4's.

I did find a difference between these older model OBX headers vs. the newer models...

"Well, this thread caused me to finally "pull the trigger" on a set of OBX SS long-tube headers that I thought were no longer available. Over two years ago (this was posted in 2010), I was looking at a set of OBX headers that included the y-pipes for the 2004-2006 F150 5.4L. They had a 3" collector and were priced at $429.00. Not a bad price... However, I procrastinated and they were replaced by a modified design, which included a tighter design at the header flange and 2.5" collectors. The new price is $495.00-$525.00. Although I liked the tighter design for clearance issues, I didn't like the price increase and I had no use for the y-pipes."

I also found these that look to be the older model OBX kits at a steep discount...

http://www.protuninglab.com/engine-h...ford-f150.html

So, since I'm not needing to bolt up to the existing cats, think I'll be okay with these older model "2WD" headers on a 4WD? Or, is it worth $300 for 2.5" collectors vs. 3" and a tighter design?

It's not ideal because the H/X/Y pipe would need to be further back in the system but I've seen installs where the drivers side crosses over behind the transfer case instead of in front of it (that would give the extra room to make the 90 to the passenger side if the collector does run too long).

 

Lots of people selling what look like the old model OBX headers (complete kits) and they're showing compatibility with both 2WD and 4WD, sort of. Maybe they don't know all FX4's are 4x4?

http://www.ebay.com/itm/TUBULAR-RACING-EXHAUST-MANIFOLDS-HEADERS-04-08-FORD-F-150-F150-XLT-FX4-5-4L-V8-/201074158966?fits=Model%3AF-150&hash=item2ed0f42d76&vxp=mtr
http://www.ebay.com/itm/STAINLESS-ST...00145f&vxp=mtr

http://www.ebay.com/itm/STAINLESS-ST...c978a7&vxp=mtr

http://www.ebay.com/itm/FOR-F-150-F1...c5335f&vxp=mtr

http://www.ebay.com/itm/FOR-04-08-FO...7825ea&vxp=mtr