V.28-29 These verses refer to something entirely different. These dead are those who are in their graves. Their body is dead. Both saved and unsaved. The believers, whose bodies are in the graves are going to be raised by the voice of the Lord Jesus one of these days (1 Thess. 4:16). The unbelievers who have died will remain in their grave for about a thousand years longer! And then they shall be raised by the voice of the Son of God (Rev. 20:12).
So our two verses refer to two separate events and two separate times.
V.32-47 They were without excuse when they refused to accept Him. Four things and persons spoke about Him to them: (1) John the Baptist, (2) His own works, (3) His Father at His baptism (John 1:32-33) and (4) the Old Testament scriptures (vvs. 45-47).