Lionel really should not have that link for the 12917 variety.
If I recall, the terminals are nothinhg like the traditional (until roughly early 90's burning switch tower variety) "4 corners of the square hole" for the contacts. I'm also thinking there might not be the hole in the bottom of the base at all, but I could be mistaken.
The terminals on the 12917 are simply lined up ina row I believe. There are small imprinted letters (I think), but at the moment I am unable to check them.
Hobo, if you can list the names of the posts, it's likely someone can help. I half think they are labeled 2 as "AC", one as "light" and one as "action", but that is from memory.
-Dave