Liquid Post does not fit on Keg

So I recently got some ball lock kegs, not really sure what they are. All I can tell is that they say Spartanburg on the side. Anyway, I wanted to replace the posts and other hardware and found what appeared to be the right shape posts online so I purchased them (they appeared identical to the ones that came with the kegs). The gas one fit completely fine, but the liquid post is too large and will not screw on. Has anyone else had this issue and does anyone know where i can find posts that would fit? These are the ones I purchased:

http://stores.kegconnection.com/Detail.bok?no=400

I didn't even realize that the threads on the two posts would be different, that seems stupid.

I recently had a similar problem. Check out Cornelius Kegs on Wikipedia. There's a great description there of the different keg types and their associated input and output threads..

Brobeman

There were several different keg manufacturers and even different models from the same manufacturer, so there are several variations for the post threading. You can't find any other identifying marks on the keg at all? You're sure it says spartanburg and not just spartan? The ones you bought look like they're for the newer firestone kegs (9/16"-18 tpi for the gas and 5/8"-18 tpi for the liquid). You could have a cornelius spartan which needs 19/32"-18 tpi for both. You might find this helpful-

http://www.dresselbrew.com/Keg_Info.htm

Just out of curiosity, what's wrong with the original posts that you're replacing them? It's very uncommon for the post itself to become damaged enough to need replacement. They usually just need new o-rings and sometimes new poppets.