My vote would be for a combined LS and LS made tractors main forum. But I can see a problem with that since the other brands (Montana, FarmTrac, New Holland, etc) all have some models made by other companies also and a few folks wouldn't know if their model is LS made or not.
Maybe an LS main forum and it's sub-forums could be "LS made Montana", "LS made FarmTrac", etc.