[whh333]

for the 2003 6.0l ICP replacement, there is a special socket you can get from a known tool maker. The exact description is:
Socket, Ford ICP Sensor, 1 1/16", 3/8" square drive

Lowe's has a socket 1 1/16" deep well socket that worked on my ICP sensor without any modification, and it was cheap. It is a Kobalt #338053. I tried to use a 1 1/16" crows foot, but had little luck after fiddling with it 30 minutes. It was a 1/2" drive very heavy piece that would not fit in the limited space.

 

[whh333]

I hope you have found it by now. It has been a while since I did this job, but I remember having to cope with a heat shield that curved back and down. My guess is that it is on the back side of the heat shield, meaning you would need to go under the truck and feel on the backside of the shield, if your arms are thin enough. A flexible rod of some sort might help if your arm cannot get up there to find it. If I am remembering correctly, you will be searching between the heat shield and the firewall.

Best of luck, I hope this helps.

whh333