The following is in response to you asking:

Please help me understand Eph.1:10. How can the re-birthed with new bodies fashioned like unto Christ's glorious body, fitted for ruling and reigning in the heavenlies, be gathered together in one with the Jew and Gentile living on planet earth?

There are a few details to answer based on the verse you reference.

Eph.1:10 That in the dispensation of the fulness of times he might gather together in one all things in Christ, both which are in heaven, and which are on earth; even in him:

The first few words of our reference verse mentions, "the dispensation of the fulness of times". This is key to the understanding (and timing) of this verse. The word "times" (plural) is referencing all the previous dispensations that came before. If you look at this chart, you will see periods of time in various categories. We have the age of antiquity (All mankind - 2000 years), then we have the program of Israel under the law, also 2000 years. Then we have the church age (The Body of Christ under grace), also 2000 years. Then we have the 7-year tribulation, and then the Millennial Kingdom for 1000 years. (Basically this is the 7000 years of time allotted to mankind). All these are referred to as "periods of time" or dispensations.

So, coming back to "the dispensation of the fulness of times", we are now referencing the next period of time AFTER the Millennial Kingdom. On the chart, this is represented by the bright yellow period called "Eternity". Notice that there is no Body of Christ and Millennial Kingdom anymore...it is merged together without distinction. So, it is in this time that the body of Christ (in the heavenlies) is brought together with God's earthly people from the Millennial Kingdom. Remember, at this time (the fulness of the times), we have reached the end of God's planned program with mankind. The Body of Christ is reigning with Christ in the heavens for the 1000 years, and the Jews (and Gentile 'sheep') have been reigning with Christ on earth for the 1000 years. Here is where there is still a divide between the two programs. But once we hit the end of the dispensations, these programs also end. The plan of God comes to a close and after Satan and his followers are destroyed at the Great White Throne Judgement, and only the righteous remain (as the glorious inheritance of Christ), there is no need to keep these two programs apart. God brings them all together. At this time there is no more Jew or Gentile identified from the Law and Grace programs, but just one family of God that enters into eternity.

See this scripture, also in Ephesians:

Eph.3:14 For this reason I bow my knees to the Father of our Lord Jesus Christ, 15 from whom the whole family in heaven and earth is named.

Notice, God's whole family. They are derived from those in heaven AND those on earth. But these are only joined together after the Millennial Kingdom, and after the Great White Throne judgement, when we will enter into eternity under a new banner, the family of God.

Hope this clarifies it a bit more for you.

PS: Just my interpretation, but note that we are not 're-birthed' (like Israel is). Rather, we are 'regenerated'. Thought I'd mention that if you want to study it up further.