Rock Opera, ridden by 55-year-old Laffit Pincay, Jr., and True Phenomenon, under Thoroughbred racing's comeback jockey of the year, Patrick Valenzuela, won divisions of the featured Oceanside Stakes today before the largest opening-day crowd in Del Mar history, 37,439.The attendance total was also Del Mar's second largest all-time, exceeded only by the 44,181 that turned out for the memorable 1996 Pacific Classic in which Cigar was upset by Dare And Go. Previous top first day crowd was 34,697 in 1994.Pincay, the sport's winningest rider, chalked up victory number 9,390 with a wire-to-wire journey astride Rock Opera, who completed the mile over a firm grass course in a stakes record time of 1:34.14 in the first division of the event for three-year-olds. Johar closed well to be second, with 6-5 favored Mountain Rage third and Sunkosi fourth in the field of six. Point Prince was a scratch from the original line-up. Rock Opera, a son of Royal Academy owned by Ballantyne and Welty and trained by Clifford Sise, earned $49,680 from a gross purse of $82,800. Well-regarded in the betting, Rock Opera paid $7.20 after his third win in four career starts. In the second division of the Oceanside Stakes, True Phenomenon, another talented runner from the barn of trainer Bobby Frankel, held off the late challenge of Dream Machine under strong handling from Valenzuela to score by a length. Diamond Hope was third, with Ecstatic fourth. True Phenomenon, a son of Afternoon Delites owned by Stonerside Stable, ran the distance in 1:34.52 and returned $l3.20 while earning $50,580 from a gross purse of $84,300. In addition to his success on Rock Opera, Pincay also won the sixth on My Friend Lumpy at $8.40 and the ninth on McAdam at $7.60 to run his world's leading total to 9,392 victories. Valenzuela, resurrecting his career after a series of setbacks in recent years, also won the day's second race on Turkish Prize at $5 to pick up where he left off at Hollywood Park where he was leading rider.