Hi Bill,

 

I think Matthew 19:27-28 tells us who 12 of the 24 elders will be.

 

Matthew 19:27-28v(NKJV)

 

27 Then Peter answered and said to Him, “See, we have left all and followed You. Therefore what shall we have?”

 

28 So Jesus said to them, “Assuredly I say to you, that in the regeneration, when the Son of Man sits on the throne of His glory, you who have followed Me will also sit on twelve thrones, judging the twelve tribes of Israel.

 

It looks to me like 12 of the 24 elders will be the 12 apostles, (excluding Judas Iscariot) who was replace by Mathias.