Thanks to all for the posts and references to earlier threads. You folks gave me everything I needed to talk intelligently to my dealer. I was a bit disappointed with him since I bought the tractor and chains (and rear blade) from him all at the same time. He shoulda told me about the spacer issue.
Anyway, at this point he's apologized, but all he can offer is to take the chains back or sell me spacers (with new studs) for $350 a set. Turns out he just go a set in, so I asked him if I could just take a look and measure them so I can make my own.
After I see them, I'll let you know what happens. I think I can get a local machine shop to make them for about half what the dealer wants. Also, I'll try to post a picture or a drawing or a source to purchase them.
Thanks y'all!
JMZ