Three Santa Fe Springs gang members received tough sentences after pleading guilty to a 1981 rape for which an innocent fellow gang member spent 3 1/2 years in prison. David Cadena, 22, and Anthony Ramirez, 26, were sentenced to 18 years, while Gregory Franco, 26, was given 16 years. David Navarro, 25, was convicted after the victim and her boyfriend identified him. The couple were at Huntington Beach State Park when seven young men beat the boyfriend senseless and repeatedly raped the woman. Navarro, however, was granted a new trial last year on grounds that the eyewitness identifications were inadequate. While free on bail awaiting his second trial, Navarro, 25, secretly tape recorded his fellow gang members admitting their guilt. Two other gang members have also pleaded guilty and await sentencing.