I bought a tilt steering column for my 1968 chevelle on Ebay and the guy swore up and down that the column was made as a one year only for a 1968 chevelle. I bought a "67-68 wood steering wheel hub" today for the column and tried to slide the hub into place and found that the hub has three small holes in it near the center mounting hole. two of the holes have threads and the third hole is not threaded......my problem is that a spring pin on the column does not line up with the non-threaded hole in the hub.
1. Does this spring pin on the column actuate the horn?
2. Am I correct in assuming this pin should line up with the non threaded hole?3. Does this mean that this is not a 1968 chevelle tilt column?
4. Is there a way to identify if this is a 68 tilt or some other tilt?

I don't think you have enough parts to complete the installation. The spring pin that you refer to is part of the turn signal switch. You need a spring and cancelling cam that slides over the steering shaft. The cancelling cam, which is plastic, has a copper surface that rides on the spring pin of the turn signal switch and a spring loaded horn contact housed in a sleeve. When the hub is installed, it pushes the cam down over the spring on the steering shaft which preloads the cam.
The hub should have two 5/16" threaded holes straight across from one another. These are used to pull the hub off the splined shaft. If you view the hub with these holes in a horizontal position, the other larger hole will either be a 7 o'clock or 1 o'clock, depending on how you are holding the hub. This "other" hole(your hole 3) alllows for the plastic sleeve of the cancelling cam to slide into the hub. There is a spring loaded horn contact that is housed in this sleeve. This contact is depressed by a tab on the horn cap retainer which is held on the hub by three small machine screws. The horn button snaps on this retainer. When the button is pressed, it makes contact with the metal retainer and completes the ground circuit and the horn sounds.
A '68 tilt column IS a one year only column. THe column is pretty short with the shaft protruding only 2"-3" below the lower bearing. The shaft should be splined for the rag joint connector. It does not have an ignition switch like the '69 and newer columns. It should have a section of it's mast jacket that looks like expanded metal. This was a new design that was first used in '67 as a safety factor for a collapsable column. The expanded metal section had a plastic cover(sheath) over it. Most rebuilt columns will not have this cover.
From your description, I think the only problem is a lack of parts.

Hope this helps!

The bowl (the part where the column mates up with the dash) is different on other A-body columns.

There's an easy way to tell if its the right one on Ebay, if its going for about $200, its not a Chevelle column, if its going for at least $350+, its the right one!

Seriously, the pic shows the difference. THe top pic shows a 68 "A body" column and the bottom pic is a '68 "Chevelle only" column. I was told that other A-bodies wouldn't work, but maybe with some "massaging" around the plastic dash piece, it "might" work.