LEXINGTON, Ky. - Sons of the Mr. Prospector stallion Gone West are the hottest properties in breeding today, and there is no wonder. Among third-crop stallions (the oldest foals only 4) this season, the two leading sires by earnings are Elusive Quality and Grand Slam, both by Gone West. They rank first and fifth in the general sire list, with two other sons of Gone West, Mr. Greeley and West by West, also in the top 50.