During gear extension for landing, the flight crew noted a 'loud & very noticeable jolting of the aircraft.' Shortly thereafter, they also noticed that a portion of the right main gear had punctured the upper surface of the right wing. The crew then declared an emergency and made an uneventful landing. An investigation revealed the right main gear actuator support link, PN 65-19657-5, had become corroded and failed. The outboard end of the main gear actuator beam then punctured the upper wing panel. Also, a hydraulic line was severed, which disabled the 'A' hydraulic system. Maintenance records from the previous aircraft owner erroneously indicated that in 1971, the failed part had been replaced with a newer link assembly, PN 19657-11, which did not require an inspection. Consequently, the required inspections specified in AD 68-17-01, regarding the failed link, had not been complied with by the new owner. Boeing had issued a service bulletin (727-32-306) which recommended that link assemblies with PN 19657-5 (as well as -4, -8 & -13) be removed from service and discarded.