This vacuum stuff can be a real pain. I've collected some photos from some other posts and modified them, in hopes that it will help you locate and identify this stray hose connection. I'll try to explain each photo...
This is a line drawing of all the vacuum hose connections. I actually printed this out and used different colored markers to fill in each vacuum line. Then I went out and verified my connections. Pretty simplistic, but it made the job itself quite easy. It's difficult to picture here, as this is sort of an X-ray drawing, but the EGR valve is mounted to the bottom of the intake manifold, as the crow flies, it's directly below the carburetor on the bottom side of the intake manifold. It's a bugger to see in there, so a good idea of what you're feeling for can really help.
This is a photo of the bottom of the cylinder head, with the exhaust (top) and intake (bottom) manifolds still attached (thanks fullaluv!). The left side of the photo would be the front of the truck. I've pointed out where the EGR valve hose connection is. When you are leaning in the engine compartment, the connection you are after is on the passenger side, near the motor mount. There is another photo of fullaluv's engine with the motor mount attached, so if you are not sure what that is, just let me know and I'll add that one here too.
Finally, a photo of a nice clean intake from underneath. Again, I've added the EGR identification. I think the easiest way to get to this is to follow the brass tube (in the top right) around with your hands until you find the EGR valve. A lot of this is going to be a 'feel' sort of job, it's almost impossible to see what you're after here. DO NOT do this when the engine is hot!
I realize the orientation of these photos can be sort of confusing, but I hope this provides some help. Just as an FYI, my experience in Cali with smog stuff has not been so good. There may be a reason someone disconnected this, when you get it hooked up the truck may run really crappy. The EGR valve is available new online for about $50-80.
Good luck