91 e350 7.3 where is the theromstat located? My hose runs to a metal pipe?

 

The metal pipe is the thermostat housing. If you follow it down to the block you will find bolts and studs holding it, 3 if IIRC. moving the alternator out of the way will give you more room to work, it is what I did. Also, be careful removing the bolts/studs. Mine were extremely rusty. I used PB Blaster for a few days and heat to get them out. Had to slowly work them back and forth. Then I cleaned them up with a wire wheel and coated them with anti-seize.

 

Also watch the wires on the alternator.
The large one is always hot with battery power, easy to short out when you are working on the thermostat.

 

Here is an excellent tutorial with lots of pictures @ oilburners on IDI thermostat replacement:

THERMOSTAT REPLACEMENT 101 Tech PicTutorial

 

This is the best advice anyone can give i learnt the hard way within a coupke seconds up it goes luckily i had an extinguisher reasonable close by but still had to rewire a fair bit.
Always remove batt cabling befor working on all vehicles.