GERRYMANDERED: The 3rd District will be a chore for county supervisors when they reapportion next year. (B1) It extends from La Habra to San Juan Capistrano and got that way in 1977, after then-Supervisor Ralph Clark decided his West Anaheim service station should be in his own 2nd District. . . . To accomplish it, he ceded the Santa Ana Canyon area to Supervisor Ralph Diedrich, who then pushed his Fullerton-based district south to the San Diego County line. Insiders said Diedrich wanted the South County development boom within his control. A not-unrelated fact: Diedrich later was convicted of exacting a bribe from a developer. Diedrich died in 1988.