I think I've pretty much confirmed it had to have been the Champion Ponies.
I totally remember those two ponies themselves and the fence. I just don't remember the trophy necessarily being clear but it's probably right. The gates, buckets and hay bales from other sets look familiar but the ponies do not so I don't think I had them. Maye a friend did or something. I think I should ask my sister if she remembers any of them too.
That's a great reference though! I was looking at Zuse's guide before but some of the pics were so small.